Wireless communication method using OFDMA random access and wireless communication terminal using same

ABSTRACT

Provided is a wireless communication terminal that wirelessly communicates with a base wireless communication terminal. The wireless communication terminal includes a transceiver, and a processor. The processor is configured to set an integer selected from a range of 0 to a value equal to or smaller than an OFDMA Contention Window (OCW) as a counter for random access, receive a trigger frame for triggering random access using one or more resource units (RUs) allocated for the random access from the base wireless communication terminal using the transceiver, decrement a value of the counter based on the one or more RUs allocated for the random access, randomly select one RU based on the one or more RUs allocated for the random access when the value of the counter is 0 or reaches 0, and attempt transmission to the base wireless communication terminal using the selected RU.

CROSS-REFERENCE TO RELATED APPLICATIONS

-   -   This application is a continuation of U.S. patent application        Ser. No. 16/452,448 filed on Jun. 25, 2019, which is a        continuation of International Patent Application No.        PCT/KR2017/015535 filed on Dec. 27, 2017, the entire contents of        which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a wireless communication method and awireless communication terminal using OFDMA random access.

BACKGROUND ART

In recent years, with supply expansion of mobile apparatuses, a wirelesscommunication technology that can provide a rapid wireless Internetservice to the mobile apparatuses has been significantly spotlighted.The wireless communication technology allows mobile apparatusesincluding a smart phone, a smart pad, a laptop computer, a portablemultimedia player, an embedded apparatus, and the like to wirelesslyaccess the Internet in home or a company or a specific service providingarea.

One of most famous wireless communication technology is wireless LANtechnology. Institute of Electrical and Electronics Engineers (IEEE)802.11 has commercialized or developed various technological standardssince an initial wireless LAN technology is supported using frequenciesof 2.4 GHz. First, the IEEE 802.11b supports a communication speed of amaximum of 11 Mbps while using frequencies of a 2.4 GHz band. IEEE802.11a which is commercialized after the IEEE 802.11b uses frequenciesof not the 2.4 GHz band but a 5 GHz band to reduce an influence byinterference as compared with the frequencies of the 2.4 GHz band whichare significantly congested and improves the communication speed up to amaximum of 54 Mbps by using an Orthogonal Frequency DivisionMultiplexing (OFDM) technology. However, the IEEE 802.11a has adisadvantage in that a communication distance is shorter than the IEEE802.11b. In addition, IEEE 802.11g uses the frequencies of the 2.4 GHzband similarly to the IEEE 802.11b to implement the communication speedof a maximum of 54 Mbps and satisfies backward compatibility tosignificantly come into the spotlight and further, is superior to theIEEE 802.11a in terms of the communication distance.

Moreover, as a technology standard established to overcome a limitationof the communication speed which is pointed out as a weak point in awireless LAN, IEEE 802.11n has been provided. The IEEE 802.11n aims atincreasing the speed and reliability of a network and extending anoperating distance of a wireless network. In more detail, the IEEE802.11n supports a high throughput (HT) in which a data processing speedis a maximum of 540 Mbps or more and further, is based on a multipleinputs and multiple outputs (MIMO) technology in which multiple antennasare used at both sides of a transmitting unit and a receiving unit inorder to minimize a transmission error and optimize a data speed.Further, the standard can use a coding scheme that transmits multiplecopies which overlap with each other in order to increase datareliability.

As the supply of the wireless LAN is activated and further, applicationsusing the wireless LAN are diversified, the need for new wireless LANsystems for supporting a higher throughput (very high throughput (VHT))than the data processing speed supported by the IEEE 802.11n has comeinto the spotlight. Among them, IEEE 802.11ac supports a wide bandwidth(80 to 160 MHz) in the 5 GHz frequencies. The IEEE 802.11ac standard isdefined only in the 5 GHz band, but initial 11ac chipsets will supporteven operations in the 2.4 GHz band for the backward compatibility withthe existing 2.4 GHz band products. Theoretically, according to thestandard, wireless LAN speeds of multiple stations are enabled up to aminimum of 1 Gbps and a maximum single link speed is enabled up to aminimum of 500 Mbps. This is achieved by extending concepts of awireless interface accepted by 802.11n, such as a wider wirelessfrequency bandwidth (a maximum of 160 MHz), more MIMO spatial streams (amaximum of 8), multi-user MIMO, and high-density modulation (a maximumof 256 QAM). Further, as a scheme that transmits data by using a 60 GHzband instead of the existing 2.4 GHz/5 GHz, IEEE 802.11ad has beenprovided. The IEEE 802.11ad is a transmission standard that provides aspeed of a maximum of 7 Gbps by using a beamforming technology and issuitable for high bit rate moving picture streaming such as massive dataor non-compression HD video. However, since it is difficult for the 60GHz frequency band to pass through an obstacle, it is disadvantageous inthat the 60 GHz frequency band can be used only among devices in ashort-distance space.

Meanwhile, in recent years, as next-generation wireless communicationtechnology standards after the 802.11ac and 802.11ad, discussion forproviding a high-efficiency and high-performance wireless communicationtechnology in a high-density environment is continuously performed. Thatis, in a next-generation wireless communication technology environment,communication having high frequency efficiency needs to be providedindoors/outdoors under the presence of high-density terminals and baseterminals and various technologies for implementing the communicationare required.

Especially, as the number of devices using a wireless communicationtechnology increases, it is necessary to efficiently use a predeterminedchannel Therefore, required is a technology capable of efficiently usingbandwidths by simultaneously transmitting data between a plurality ofterminals and base terminals.

DISCLOSURE Technical Problem

An object of an embodiment of the present invention is to provide awireless communication terminal using OFDMA random access.

Technical Solution

According to an embodiment of the present invention, a wirelesscommunication terminal that wirelessly communicates with a base wirelesscommunication terminal includes a transceiver, and a processor. Theprocessor is configured to set an integer selected from a range of 0 toa value equal to or smaller than an OFDMA Contention Window (OCW) as acounter for random access, receive a trigger frame for triggering randomaccess using one or more resource units (RUs) allocated for randomaccess from the base wireless communication terminal using thetransceiver, decrement a value of the counter based on the one or moreRUs allocated for the random access, randomly select one RU based on theone or more RUs allocated for the random access when the value of thecounter is 0 or reaches 0, and attempt transmission to the base wirelesscommunication terminal using the selected RU. In this case, the RU is agroup of a plurality of subcarriers usable for uplink transmission anddownlink transmission.

The processor may be configured to decrement the value of the counterbased on the one or more RUs allocated for the random access and acapability of the wireless communication terminal.

The processor may be configured to decrement the value of the counter bythe number of RUs through which the wireless communication terminal iscapable of transmitting a TB PPDU according to the capability of thewireless communication terminal among the one or more RUs allocated forthe random access.

When the value of the counter is 0 or reaches 0, the processor may beconfigured to randomly select any one of RUs that are allocated for therandom access and through which the wireless communication terminal iscapable of transmitting a TB PPDU according to the capability of thewireless communication terminal.

The capability of the wireless communication terminal includes acapability related to a bandwidth through which the wirelesscommunication terminal is capable of performing transmission.

The capability of the wireless communication terminal may include acapability related to a length of a padding field included in the TBPPDU.

The capability of the wireless communication terminal may include acapability related to a modulation and coding scheme with which thewireless communication terminal is capable of performing transmission.

The wireless communication terminal may be a wireless communicationterminal unassociated with the base wireless communication terminal. Theprocessor may be configured to set an OCW minimum value, which is aparameter indicating a minimum value of an OCW, to a value predeterminedas a default value of the OCW minimum value, and set an OCW maximumvalue, which is a parameter indicating a maximum value of an OCW, to avalue predetermined as a default value of the OCW maximum value. In thiscase, the value predetermined as the default value of the OCW minimumvalue and the value predetermined as the default value of the OCWmaximum value may not be values designated by the base wirelesscommunication terminal.

The wireless communication terminal may be a wireless communicationterminal unassociated with the base wireless communication terminal.When the wireless communication terminal communicates with a differentbase wireless communication terminal different from the base wirelesscommunication terminal, the processor may be configured to initialize aparameter for random access to the different wireless communicationterminal. In this case, the parameter for the random access may includethe counter, an OCW minimum value, which is a parameter indicating aminimum value of the OCW, and an OCW maximum value, which is a parameterindicating a maximum value of the OCW.

When the wireless communication terminal communicates with the basewireless communication terminal, the processor may be configured to setthe OCW minimum value and the OCW maximum value according to informationreceived from the base wireless communication terminal. In this case,when the wireless communication terminal communicates with the differentbase wireless communication terminal, the processor may be configured toset the OCW minimum value and the OCW maximum value according toinformation received from the different base wireless communicationterminal.

The wireless communication terminal is associated with the base wirelesscommunication terminal. In this case, the processor may be configured toset an OCW minimum value, which is a parameter indicating the minimumvalue of the OCW, and an OCW maximum value, which is a parameterindicating the maximum value of the OCW, according to informationreceived from a base wireless communication terminal different from thebase wireless communication terminal. In addition, the different basewireless communication terminal may belong to a multiple Basic ServiceSet Identification (BSSID) set to which the base wireless communicationterminal belongs.

The processor may be configure not to decrement the value of the counterbased on a trigger frame transmitted from the different base wirelesscommunication terminal.

The different base wireless communication terminal may be a basewireless communication terminal operating a BSS corresponding to atransmitted Basic Service Set Identification (BSSID) of the multipleBSSID set.

The information received from the different base wireless communicationterminal may not be information indicated in a signaling field allocatedfor a BSS including the wireless communication terminal.

When the trigger frame indicates an uplink transmission of the wirelesscommunication terminal, the processor may be configured not to decrementthe value of the counter based on the trigger frame.

According to an embodiment of the present invention, a method ofoperating a wireless communication terminal wirelessly communicatingwith a base wireless communication terminal includes: setting an integerselected from a range of 0 to a value equal to or smaller than an OFDMAContention Window (OCW) as a counter for random access, receiving atrigger frame for triggering random access using one or more resourceunits (RUs) allocated for the random access from the base wirelesscommunication terminal, decrementing a value of the counter based on theone or more RUs allocated for the random access, randomly selecting oneRU based on the one or more RUs allocated for the random access when thevalue of the counter is 0 or reaches 0, and attempting transmission tothe base wireless communication terminal using the selected RU. In thiscase, the RU is a group of a plurality of subcarriers useable for OFDMcommunication.

The decrementing the value of the counter may include decrementing thevalue of the counter based on the one or more RUs allocated for therandom access and the capability of the wireless communication terminal.

The decrementing the value of the counter based on the one or more RUsallocated for the random access and the capability of the wirelesscommunication terminal may include decrementing the value of the counterby the number of RUs through which the wireless communication terminalis capable of transmitting a TB PPDU according to the capability of thewireless communication terminal among the one or more RUs allocated forthe random access.

The randomly selecting the one or more RUs allocated for the randomaccess may include randomly selecting any one of RUs, which areallocated for the random access and through which the wirelesscommunication terminal is capable of transmitting a TB PPDU accordingthe capability of the wireless communication terminal.

The wireless communication terminal may be a wireless communicationterminal unassociated with the base wireless communication terminal. Theoperation method may further includes: setting an OCW minimum value,which is a parameter indicating a minimum value of the OCW, to a valuepredetermined as a default value of the OCW minimum value, and settingan OCW maximum value, which is a parameter indicating a maximum value ofthe OCW, to a value predetermined as a default value of the OCW maximumvalue. In addition, the value predetermined as the default value of theOCW minimum value and the value predetermined as the default value ofthe OCW maximum value may not be values designated by the base wirelesscommunication terminal.

Advantageous Effects

An embodiment of the present invention provides a wireless communicationmethod using OFDMA random access and a wireless communication terminalusing the same.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a wireless LAN system according to an embodiment of thepresent invention.

FIG. 2 shows a wireless LAN system according to another embodiment ofthe present invention.

FIG. 3 shows a block diagram illustrating a configuration of a stationaccording to an embodiment of the inventive concept.

FIG. 4 shows a block diagram illustrating a configuration of an accesspoint according to an embodiment of the present invention.

FIG. 5 shows a process that a station sets an access point and a linkaccording to an embodiment of the present invention.

FIG. 6 shows UL MU transmission of a wireless communication terminalaccording to an embodiment of the present invention.

FIG. 7 shows a specific trigger frame format according to an embodimentof the present invention.

FIG. 8 shows a specific format of the Common Info field and the UserInfo field of the trigger frame according to an embodiment of thepresent invention.

FIG. 9 shows the random access operation of a wireless communicationterminal according to an embodiment of the present invention.

FIG. 10 shows a specific format of the UORA parameter set elementaccording to an embodiment of the present invention.

FIG. 11 shows a specific format of a multiple BSSID element according toan embodiment of the present invention.

FIGS. 12 to 13 show a random access operation of a wirelesscommunication terminal associated with multiple BSSID sets according toan embodiment of the present invention.

FIG. 14 shows types of RUs and subcarrier indexes that may be used whentransmitting a PPDU having a 20 Mhz bandwidth according to an embodimentof the present invention.

FIG. 15 shows types of RUs and subcarrier indexes that may be used whentransmitting a PPDU having a 40 Mhz bandwidth according to an embodimentof the present invention.

FIG. 16 shows types of RUs and subcarrier indexes that may be used whentransmitting a PPDU having an 80 Mhz bandwidth according to anembodiment of the present invention.

FIG. 17 shows an encoding value used for indicating an RU in an RUAllocation subfield of a trigger frame according to an embodiment of thepresent invention.

FIGS. 18 to 19 show operations in which a wireless communicationterminal supporting only a PPDU having a bandwidth of 20 Mhz performsrandom access according to an embodiment of the present invention.

FIGS. 20 to 21 show operations in which a wireless communicationterminal supporting only a PPDU having a bandwidth of 80 Mhz or lessperforms random access according to an embodiment of the presentinvention.

FIG. 22 shows the random access operation of an unassociated wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 23 shows the random access operation of an unassociated wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 24 shows the random access operation of an unassociated wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 25 shows the random access operation of an unassociated wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 26 shows a random access operation of a wireless communicationterminal when a wireless communication terminal according to anembodiment of the present invention schedules uplink transmission by atrigger frame. FIG. 27 shows a legacy PPDU format according to anembodiment of the present invention.

FIG. 28 shows a non-legacy PPDU format according to an embodiment of thepresent invention.

FIG. 29 shows the coverage of the HE extended range SU PPDU and thetransmission coverage of the legacy PPDU according to the embodiment ofthe present invention.

FIG. 30 shows a dual beacon transmission operation of the base wirelesscommunication terminal according to an embodiment of the presentinvention.

FIG. 31 shows a format of a BSS Color Change Announcement elementaccording to an embodiment of the present invention.

FIG. 32 shows a BSS color changing operation of a base wirelesscommunication terminal when the base wireless communication terminaluses dual beacons according to an embodiment of the present invention.

FIG. 33 shows a BSS color changing operation of a base wirelesscommunication terminal when the base wireless communication terminaluses dual beacons according to another embodiment of the presentinvention.

FIG. 34 shows a BSS color changing operation of a base wirelesscommunication terminal when the base wireless communication terminaluses dual beacons according to another embodiment of the presentinvention.

FIG. 35 shows a format of an A-MPDU according to an embodiment of thepresent invention.

FIG. 36 shows a concrete format of BlockAck according to an embodimentof the present invention.

FIG. 37 shows a Per STA Info subfield according to an embodiment of thepresent invention.

FIG. 38 shows the context of a Per STA Info subfield according to anembodiment of the present invention.

FIGS. 39 to 40 show an A-MPDU configuration according to an embodimentof the present invention.

FIG. 41 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described belowin more detail with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstructed as limited to the embodiments set forth herein. Parts notrelating to description are omitted in the drawings in order to clearlydescribe the present invention and like reference numerals refer to likeelements throughout.

Furthermore, when it is described that one comprises (or includes orhas) some elements, it should be understood that it may comprise (orinclude or has) only those elements, or it may comprise (or include orhave) other elements as well as those elements if there is no specificlimitation.

This application claims priority to and the benefit of Korean PatentApplication Nos. 10-2016-0179781 (2016.12.27), Nos. 10-2017-0000020(2017.01.02), Nos. 10-2017-0000437 (2017.01.02), Nos. 10-2017-0002195(2017.01.06), and Nos. 10-2017-0002720 (2017.01.09) filed in the KoreanIntellectual Property Office and the embodiments and mentioned itemsdescribed in the respective applications are included in the DetailedDescription of the present application.

FIG. 1 is a diagram illustrating a wireless communication systemaccording to an embodiment of the present invention. For convenience ofdescription, an embodiment of the present invention is described throughthe wireless LAN system. The wireless LAN system includes one or morebasic service sets (BSS) and the BSS represents a set of apparatuseswhich are successfully synchronized with each other to communicate witheach other. In general, the BSS may be classified into an infrastructureBSS and an independent BSS (IBSS) and FIG. 1 illustrates theinfrastructure BSS between them.

As illustrated in FIG. 1, the infrastructure BSS (BSS1 and BSS2)includes one or more stations STA1, STA2, STA3, STA4, and STAS, accesspoints PCP/AP-1 and PCP/AP-2 which are stations providing a distributionservice, and a distribution system (DS) connecting the multiple accesspoints PCP/AP-1 and PCP/AP-2.

The station (STA) is a predetermined device including medium accesscontrol (MAC) following a regulation of an IEEE 802.11 standard and aphysical layer interface for a wireless medium, and includes both anon-access point (non-AP) station and an access point (AP) in a broadsense. Further, in the present specification, a term ‘terminal’ may beused to refer to a concept including a wireless LAN communication devicesuch as non-AP STA, or an AP, or both terms. A station for wirelesscommunication includes a processor and a transceiver and according tothe embodiment, may further include a user interface unit and a displayunit. The processor may generate a frame to be transmitted through awireless network or process a frame received through the wirelessnetwork and besides, perform various processing for controlling thestation. In addition, the transceiver is functionally connected with theprocessor and transmits and receives frames through the wireless networkfor the station.

The access point (AP) is an entity that provides access to thedistribution system (DS) via wireless medium for the station associatedtherewith. In the infrastructure BSS, communication among non-APstations is, in principle, performed via the AP, but when a direct linkis configured, direct communication is enabled even among the non-APstations. Meanwhile, in the present invention, the AP is used as aconcept including a personal BSS coordination point (PCP) and mayinclude concepts including a centralized controller, a base station(BS), a node-B, a base transceiver system (BTS), and a site controllerin a broad sense.

A plurality of infrastructure BSSs may be connected with each otherthrough the distribution system (DS). In this case, a plurality of BSSsconnected through the distribution system is referred to as an extendedservice set (ESS).

FIG. 2 illustrates an independent BSS which is a wireless communicationsystem according to another embodiment of the present invention. Forconvenience of description, another embodiment of the present inventionis described through the wireless LAN system. In the embodiment of FIG.2, duplicative description of parts, which are the same as or correspondto the embodiment of FIG. 1, will be omitted.

Since a BSS3 illustrated in FIG. 2 is the independent BSS and does notinclude the AP, all stations STA6 and STAT are not connected with theAP. The independent BSS is not permitted to access the distributionsystem and forms a self-contained network. In the independent BSS, therespective stations STA6 and STAT may be directly connected with eachother.

FIG. 3 is a block diagram illustrating a configuration of a station 100according to an embodiment of the present invention.

As illustrated in FIG. 3, the station 100 according to the embodiment ofthe present invention may include a processor 110, a transceiver 120, auser interface unit 140, a display unit 150, and a memory 160.

First, the transceiver 120 transmits and receives a wireless signal suchas a wireless LAN physical layer frame, or the like and may be embeddedin the station 100 or provided as an exterior. According to theembodiment, the transceiver 120 may include at least one transmit andreceive module using different frequency bands. For example, thetransceiver 120 may include transmit and receive modules havingdifferent frequency bands such as 2.4 GHz, 5 GHz, and 60 GHz. Accordingto an embodiment, the station 100 may include a transmit and receivemodule using a frequency band of 6 GHz or more and a transmit andreceive module using a frequency band of 6 GHz or less. The respectivetransmit and receive modules may perform wireless communication with theAP or an external station according to a wireless LAN standard of afrequency band supported by the corresponding transmit and receivemodule. The transceiver 120 may operate only one transmit and receivemodule at a time or simultaneously operate multiple transmit and receivemodules together according to the performance and requirements of thestation 100. When the station 100 includes a plurality of transmit andreceive modules, each transmit and receive module may be implemented byindependent elements or a plurality of modules may be integrated intoone chip.

Next, the user interface unit 140 includes various types of input/outputmeans provided in the station 100. That is, the user interface unit 140may receive a user input by using various input means and the processor110 may control the station 100 based on the received user input.Further, the user interface unit 140 may perform output based on acommand of the processor 110 by using various output means.

Next, the display unit 150 outputs an image on a display screen. Thedisplay unit 150 may output various display objects such as contentsexecuted by the processor 110 or a user interface based on a controlcommand of the processor 110, and the like. Further, the memory 160stores a control program used in the station 100 and various resultingdata. The control program may include an access program required for thestation 100 to access the AP or the external station.

The processor 110 of the present invention may execute various commandsor programs and process data in the station 100. Further, the processor110 may control the respective units of the station 100 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 110 may execute the program foraccessing the AP stored in the memory 160 and receive a communicationconfiguration message transmitted by the AP. Further, the processor 110may read information on a priority condition of the station 100 includedin the communication configuration message and request the access to theAP based on the information on the priority condition of the station100. The processor 110 of the present invention may represent a maincontrol unit of the station 100 and according to the embodiment, theprocessor 110 may represent a control unit for individually controllingsome component of the station 100, for example, the transceiver 120, andthe like. The processor 110 may be a modulator and/or demodulator whichmodulates wireless signal transmitted to the transceiver 120 anddemodulates wireless signal received from the transceiver 120. Theprocessor 110 controls various operations of wireless signaltransmission/reception of the station 100 according to the embodiment ofthe present invention. A detailed embodiment thereof will be describedbelow.

The station 100 illustrated in FIG. 3 is a block diagram according to anembodiment of the present invention, where separate blocks areillustrated as logically distinguished elements of the device.Accordingly, the elements of the device may be mounted in a single chipor multiple chips depending on design of the device. For example, theprocessor 110 and the transceiver 120 may be implemented while beingintegrated into a single chip or implemented as a separate chip.Further, in the embodiment of the present invention, some components ofthe station 100, for example, the user interface unit 140 and thedisplay unit 150 may be optionally provided in the station 100.

FIG. 4 is a block diagram illustrating a configuration of an AP 200according to an embodiment of the present invention.

As illustrated in FIG. 4, the AP 200 according to the embodiment of thepresent invention may include a processor 210, a transceiver 220, and amemory 260. In FIG. 4, among the components of the AP 200, duplicativedescription of parts which are the same as or correspond to thecomponents of the station 100 of FIG. 2 will be omitted.

Referring to FIG. 4, the AP 200 according to the present inventionincludes the transceiver 220 for operating the BSS in at least onefrequency band. As described in the embodiment of FIG. 3, thetransceiver 220 of the AP 200 may also include a plurality of transmitand receive modules using different frequency bands. That is, the AP 200according to the embodiment of the present invention may include two ormore transmit and receive modules among different frequency bands, forexample, 2.4 GHz, 5 GHz, and 60 GHz together. Preferably, the AP 200 mayinclude a transmit and receive module using a frequency band of 6 GHz ormore and a transmit and receive module using a frequency band of 6 GHzor less. The respective transmit and receive modules may performwireless communication with the station according to a wireless LANstandard of a frequency band supported by the corresponding transmit andreceive module. The transceiver 220 may operate only one transmit andreceive module at a time or simultaneously operate multiple transmit andreceive modules together according to the performance and requirementsof the AP 200.

Next, the memory 260 stores a control program used in the AP 200 andvarious resulting data. The control program may include an accessprogram for managing the access of the station. Further, the processor210 may control the respective units of the AP 200 and control datatransmission/reception among the units. According to the embodiment ofthe present invention, the processor 210 may execute the program foraccessing the station stored in the memory 260 and transmitcommunication configuration messages for one or more stations. In thiscase, the communication configuration messages may include informationabout access priority conditions of the respective stations. Further,the processor 210 performs an access configuration according to anaccess request of the station. The processor 210 may be a modulatorand/or demodulator which modulates wireless signal transmitted to thetransceiver 220 and demodulates wireless signal received from thetransceiver 220. The processor 210 controls various operations such asradio signal transmission/reception of the AP 200 according to theembodiment of the present invention. A detailed embodiment thereof willbe described below.

FIG. 5 is a diagram schematically illustrating a process in which a STAsets a link with an AP.

Referring to FIG. 5, the link between the STA 100 and the AP 200 is setthrough three steps of scanning, authentication, and association in abroad way. First, the scanning step is a step in which the STA 100obtains access information of BSS operated by the AP 200. A method forperforming the scanning includes a passive scanning method in which theAP 200 obtains information by using a beacon message (S101) which isperiodically transmitted and an active scanning method in which the STA100 transmits a probe request to the AP (S103) and obtains accessinformation by receiving a probe response from the AP (S105).

The STA 100 that successfully receives wireless access information inthe scanning step performs the authentication step by transmitting anauthentication request (S107 a) and receiving an authentication responsefrom the AP 200 (S107 b). After the authentication step is performed,the STA 100 performs the association step by transmitting an associationrequest (S109 a) and receiving an association response from the AP 200(S109 b).

Meanwhile, an 802.1X based authentication step (S111) and an IP addressobtaining step (S113) through DHCP may be additionally performed. InFIG. 5, the authentication server 300 is a server that processes 802.1Xbased authentication with the STA 100 and may be present in physicalassociation with the AP 200 or present as a separate server.

In a specific embodiment, the AP 200 may be a wireless communicationterminal that allocates a communication medium resource and performsscheduling in an independent network, such as an ad-hoc network, whichis not connected to an external distribution service. In addition, theAP 200 may be at least one of a base station, an eNB, and a transmissionpoint TP. The AP 200 may also be referred to as a base wirelesscommunication terminal.

The base wireless communication terminal may be a wireless communicationterminal that allocates and schedules medium resources in communicationwith a plurality of wireless communication terminals. Specifically, thebase wireless communication terminal may serve as a cell coordinator. Ina specific embodiment, the base wireless communication terminal may be awireless communication terminal that allocates and schedulescommunication medium resources in an independent network, such as anad-hoc network, that is not connected to an external distributionservice.

The base wireless communication terminal may simultaneously communicatewith a plurality of wireless communication terminals using OrthogonalFrequency Division Multiple Access (OFDMA) or Multi-user Multiple InputMultiple Output (MU-MIMO). In this case, the base wireless communicationterminal may transmit trigger information to a plurality of wirelesscommunication terminals to trigger uplink (UL) multi-user (MU)transmission using OFDMA of the plurality of wireless communicationterminals. This will be described with reference to FIG. 6.

FIG. 6 shows UL MU transmission of a wireless communication terminalaccording to an embodiment of the present invention.

The base wireless communication terminal may transmit triggerinformation to a plurality of wireless communication terminals totrigger UL MU transmission of the plurality of wireless communicationterminals. Specifically, the base wireless communication terminal maytransmit trigger information to a plurality of wireless communicationterminals to trigger the plurality of wireless communication terminalsto simultaneously transmit an immediate response frame. In this case,the immediate response may indicate that the response frame istransmitted within a predetermined time from when the triggerinformation is received in the same Transmission Opportunity (TXOP). Inthis case, the predetermined time may be a Short Inter-Frame Space(SIFS) defined in the 802.11 standard. The base wireless communicationterminal can transmit the trigger information using the trigger frame.Also, the base wireless communication terminal may transmit the triggerinformation using the MAC header.

A plurality of wireless communication terminals may transmit a responseframe for trigger information using a trigger based (TB) PPDU. In thiscase, the plurality of wireless communication terminals may transmit theTB PPDU after a predetermined time from when the trigger information isreceived. In addition, the plurality of wireless communication terminalsmay transmit the TB PPDU using at least one of UL OFDMA and UL MU-MIMO.When the trigger type of the trigger information is transmitted throughan MU-Request To Send (RTS) frame, a plurality of wireless communicationterminals can transmit a response frame for an MU-RTS frame using anon-HT PPDU.

In the embodiment of FIG. 6, the AP transmits a trigger frame to thefirst station STA1, the second station STA2, the third station STA3, andthe fourth station STA4. The first station STA1, the second stationSTA2, the third station STA3, and the fourth station STA4 receive atrigger frame. The first station STA1, the second station STA2, thethird station STA3 and the fourth station STA4 transmit a HEtrigger-based PPDU (TB PPDU) when the SIFS elapses from when the triggerframe is received. The AP receives the HE trigger-based PPDU (TB PPDU)and transmits an ACK to the first station STA1, the second station STA2,the third station STA3 and the fourth station STA4.

As described above, the base wireless communication terminal maytransmit trigger information using a trigger frame or a MAC header.Specifically, the base wireless communication terminal may transmit thetrigger information using the UL MU Response Scheduling (UMRS) A-Controlsubfield of the MAC header. In a specific embodiment, the wirelesscommunication terminal receiving the MAC frame including the UMRSA-Control subfield transmits the TB PPDU in response to the UMRSA-Control subfield. Also, the wireless communication terminal indicatedby the User Info field of the trigger frame may transmit the TB PPDU inresponse to the trigger frame. A specific format of the trigger framewill be described in detail with reference to FIG. 7.

FIG. 7 shows a specific trigger frame format according to an embodimentof the present invention.

The trigger frame may include at least one of a Frame Control field, aDuration field, an RA field, a TA field, a Common Info field, a UserInfo field, a Padding field, and an FCS field. Depending on the triggertype, the response which is requested by the trigger frame may vary. Inaddition, the field included in the trigger frame may vary depending onthe trigger type.

The RA field indicates the receiver address of the trigger frame. Whenthe trigger frame triggers the transmission of one wirelesscommunication terminal, the RA field may indicate the MAC address of thecorresponding wireless communication terminal. When the trigger frametriggers the transmission of two or more wireless communicationterminals, the RA field may indicate a broadcast address. When thetrigger type of the trigger frame is GCR MU-BAR, the RA field mayindicate a group address corresponding to a plurality of wirelesscommunication terminals triggered by the trigger frame.

The TA field indicates the transmitter address of the trigger frame.When the wireless communication terminal transmitting the trigger framedoes not use the multiple BSSID, the TA field may indicate the MACaddress of the wireless communication terminal transmitting the triggerframe. In addition, when a wireless communication terminal transmittinga trigger frame uses multiple BSSIDs and the trigger frame triggers aplurality of wireless communication terminals of a multiple BSSID set,the TA field may indicate the transmitted BSSID of the multiple BSSIDset to which the wireless communication terminal transmitting thetrigger frame belongs. In this case, the transmitted BSSID indicates aBSS that may signal information on other BSS included in the multipleBSSID set. The identifier of the BSS that does not correspond to thetransmitted BSSID among the BSSs included in the multiple BSSID set is anontransmitted BSSID. Specifically, the base wireless communicationterminal operating the BSS corresponding to the transmitted BSSID maysignal information on the BSS corresponding to the nontransmitted BSSIDusing the multiple BSSID elements. The management frame transmitted fromthe BSS corresponding to the transmitted BSSID may include multipleBSSID elements. In this case, the management frame may include a beaconframe and a probe response frame. In addition, the transmitted BSSID maybe present for each multiple BSSID set. This will be described in moredetail with reference to FIG. 11.

The Common Info field indicates information commonly required for atleast one wireless communication terminal triggered by the trigger frameto transmit a response to the trigger frame. The User Info fieldindividually indicates information required for each of the plurality ofwireless communication terminals indicated by the trigger frame totransmit a response to the trigger frame. Specifically, the triggerframe may include a plurality of User Info fields. A specific format ofthe Common field and the User Info field will be described withreference to FIG. 8.

The Padding field includes a padding bit. Specifically, the Paddingfield may help secure a time for the wireless communication terminaltransmitting the response frame to the trigger frame to prepare for theresponse frame transmission. Therefore, the length of the Padding fieldmay be determined according to the capability of the wirelesscommunication terminal transmitting the response frame to the triggerframe. Also, the trigger frame may not include the Padding field. ThePadding field may indicate the start of the Padding field with apredetermined value. In this case, the predetermined value may be 0xFFF.In addition, the remaining fields of the Padding field other than thePadding field including the predetermined value may include a valueother than the predetermined value or a predetermined value.

The specific format of the trigger frame may be the same as that of theembodiment of FIG. 7.

FIG. 8 shows a specific format of the Common Info field and the UserInfo field of the trigger frame according to an embodiment of thepresent invention.

Specifically, the format of the Common Info field and the format of theUser Info field according to an embodiment of the present invention maybe the same as those shown in FIGS. 8(a) and 8(b), respectively. TheUser Info field may indicate a wireless communication terminal triggeredby the trigger frame. Specifically, when the User Info field includesthe Association Identifier (AID) of the wireless communication terminalor a part of the AID, the wireless communication terminal correspondingto the AID may determine that the trigger frame triggers the wirelesscommunication terminal. In a specific embodiment, the AID12 subfield inthe User Info field may indicate 12 Least Significant Bits (LSBs) of theAID of the wireless communication terminal triggered by the triggerframe.

In addition, the User Info field may indicate a resource unit (RU)allocated to a wireless communication terminal triggered by the triggerframe. The RU may indicate that a plurality of subcarriers that may beuseable for uplink and downlink transmission are grouped according tothe size of the frequency band. In this case, in the uplink transmissionand the downlink transmission, at least one of OFDM, OFDMA, and MU-MIMOmay be used. Also, the grouping may be referred to as subchannelization.In a specific embodiment, the RU Allocation subfield may indicate an RUallocated to a wireless communication terminal indicated by the AID12subfield.

The base wireless communication terminal may trigger the uplinktransmission of an arbitrary wireless communication terminal using thetrigger frame. Specifically, the base wireless communication terminalmay trigger random access to the designated RU. In this case, the basewireless communication terminal may set the User Info field of thetrigger frame to indicate a predetermined value instead of the AID ofthe specific wireless communication terminal. In a specific embodiment,the base wireless communication terminal may set the AID12 subfield ofthe User Info field of the trigger frame to a predetermined value. Inaddition, when the User Info field of the trigger frame indicates apredetermined value instead of the AID of the specific wirelesscommunication terminal, the wireless communication terminal receivingthe trigger frame can randomly access the RU indicated by thecorresponding User Info field. In a specific embodiment, when the AID12subfield of the User Info field of the trigger frame received by thewireless communication terminal indicates a predetermined value, thewireless communication terminal randomly accesses the RU indicated bythe RU Allocation subfield of the corresponding User Info field. Thepredetermined value may be 0. In addition, the predetermined value maybe 2045. A specific operation in which the wireless communicationterminal performs random access based on the trigger frame will bedescribed with reference to FIG. 9.

FIG. 9 shows the random access operation of a wireless communicationterminal according to an embodiment of the present invention.

The wireless communication terminal may perform an OFDMA random accessoperation through the following operations. The wireless communicationterminal selects an arbitrary integer within the OFDMA contention window(OCW). Specifically, the wireless communication terminal may select arandom integer in a range from 0 to a value equal to or smaller than theOCW. In this case, the OCW may be equal to or greater than the OCWminimum value OCWmin, or may be equal to or less than the OCW maximumvalue OCWmax, which is a positive integer. The wireless communicationterminal sets the selected number to an OFDMA random access backoff(OBO) counter. The wireless communication terminal may receive thetrigger frame and decrement the OBO counter based on the RU which thetrigger frame indicates for the random access. Specifically, thewireless communication terminal may receive the trigger frame anddecrement the OBO counter by the number of RUs in which the triggerframe indicates the random access. When the OBO counter is 0 or the OBOcounter reaches 0, the wireless communication terminal may randomlyselect any one of the RUs indicated for the random access and attempttransmission through the selected RU. In this case, the wirelesscommunication terminal may determine whether the selected RU is idle,and may transmit a pending frame for a base wireless communicationterminal to the base wireless communication terminal through theselected RU when the selected RU is idle. In addition, when the wirelesscommunication terminal determines that the corresponding RU isdetermined to be busy by either a physical carrier sense or a virtualcarrier sense, the wireless communication terminal may determine thatthe corresponding RU is busy. The physical carrier sense may include aClear Channel Assessment (CCA). In addition, the physical carrier sensemay include an energy detection (ED). When it is determined that the RUselected by the wireless communication terminal is busy, the wirelesscommunication terminal may maintain the OBO counter as 0 withouttransmitting a pending frame to the base wireless communication.

The wireless communication terminal may set OCWmin and OCWmax accordingto the OBO-related parameter value signaled by the base wirelesscommunication terminal associated with the wireless communicationterminal. Also, when the wireless communication terminal attempts randomaccess for the first time, the wireless communication terminal receivesthe OBO-related parameter signaled by the base wireless communicationterminal, or the wireless communication terminal succeeds intransmission through the random access, the wireless communicationterminal may be allowed to initialize the OBO procedure. In this case,the initialization of the OBO procedure may include at least one of theinitialization of the OBO counter and the initialization of the OCW.Further, when the wireless communication terminal initializes the OCW,the wireless communication terminal may set the OCW to OCWmin. When thetransmission through the random access of the wireless communicationterminal fails, the wireless communication terminal may update the valueof OCW to (2×OCW+1). In this case, the wireless communication terminalselects a random integer in the updated OCW, and sets the random integerselected as the OBO counter. Further, when the value of the OCW reachesOCWmax, the wireless communication terminal may maintain the OCW asOCWmax even if the transmission through the random access of thewireless communication terminal fails.

In the embodiment of FIG. 9, the OBO counter of the first station STA1is 5 and the OBO counter of the second station STA2 is 1. The APtransmits a trigger frame that triggers a random access for the first RURU 1 and the second RU RU 2. Since the number of RUs allocated forrandom access is 2, the first station STA1 decrements the OBO counter by2 and sets the OBO counter to 3, and the second station STA2 sets theOBO counter to 0. Since the OBO counter of the second station STA2becomes 0, the second station STA2 randomly selects any one of the firstRU RU 1 and the second RU RU 2 allocated for random access and attemptstransmission. After SIFS from when the second station STA2 receives thetrigger frame, the second station STA2 transmits the TB PPDU to the APthrough the randomly selected RU. The AP receives the TB PPDU from thesecond station STA2. After SIFS from when the AP receives the TB PPDU,the AP transmits an ACK for the frame transmitted by the second stationto the second station.

The second station STA2 whose transmission for the AP is successfullysets OCW to OCWmin and selects an arbitrary number within the set OCW.In this case, the second station STA2 selects 6 and sets 6 as the OBOcounter. The AP transmits a trigger frame that triggers a random accessto the first RU RU 1, the second RU RU 2, and the third RU RU 3. Sincethe number of RUs allocated for random access is 3, the first stationSTA1 decrements the OBO counter by 3 and sets it to 0, and the secondstation STA2 decrements the OBO counter by 3 and sets it to 3. Since theOBO counter of the first station STA1 becomes 0, the first station STA1arbitrarily selects any one of the first RU RU 1, the second RU RU 2,and the third RU RU 3, in which a trigger is allocated for randomaccess, and attempts transmission. After SIFS from when the firststation STA1 receives the trigger frame, the first station STA1transmits the TB PPDU to the AP through the arbitrarily selected RU. TheAP receives the TB PPDU from the first station STA1. After SIFS fromwhen the AP receives the TB PPDU, the AP transmits an ACK for the frametransmitted by the first station to the first station.

As described above, the wireless communication terminal may set OCWminand OCWmax according to the OBO-related parameter value signaled by thebase wireless communication terminal associated with the wirelesscommunication terminal. Specifically, the wireless communicationterminal may receive an element including an OBO-related parameter valuefrom a base wireless communication terminal associated with the wirelesscommunication terminal. In this case, the element may be referred to asa UL OFDMA-based Random Access (UORA) parameter set element. A specificformat of the UORA parameter set element will be described withreference to FIG. 10.

FIG. 10 shows a specific format of the UORA parameter set elementaccording to an embodiment of the present invention.

The UORA parameter set element may include an Element ID field, a Lengthfield, an Element ID Extension field, and an OCW Range field. TheElement ID field indicates an element identifier that identifies theUORA parameter set element. The Length field indicates the length of theUORA element. The Element ID Extension field indicates an extension IDthat is combined with an element ID to make an extended ID of the UORAparameter set element. The OCW Range field indicates information on therange of the OCW.

The OCW Range field may include information on OCWmin and OCWmax.Specifically, the OCW Range field may include an EOCWmin field, anEOCWmax field, and a Reserved field. In this case, the wirelesscommunication terminal may set the OCWmin according to the valueindicated by the EOCWmin field. In a specific embodiment, the wirelesscommunication terminal may set OCWmin to 2EOCWmin−1. Further, thewireless communication terminal may set OCWmax according to the valueindicated by the EOCWmax field. In a specific embodiment, the wirelesscommunication terminal may set OCWmax to 2EOCWmax−1.

The wireless communication terminal may set OCWmin and OCWmax accordingto the most recently received UORA parameter set element. In addition,the wireless communication terminal may set OCWmin and OCWmax accordingto the most recently received UORA parameter set element regardless ofthe Access Category (AC) of the traffic to be transmitted. The basewireless communication terminal may transmit a UORA parameter setelement using a beacon frame. Also, the base wireless communicationterminal may transmit a UORA parameter set element using a proberesponse frame.

The specific format of the UORA parameter set element may be the same asthat in FIG. 10.

When there are a plurality of physical access points in one network, dueto the management frames transmitted by the plurality of access points,the time for the frame for data transmission to occupy the channel maybe very short. Therefore, one base wireless communication terminal canoperate a plurality of BSSs in network. This will be described withreference to FIG. 11.

FIG. 11 shows a specific format of a multiple BSSID element according toan embodiment of the present invention.

The base wireless communication terminal may transmit one managementframe to signal information on a plurality of BSSs. Specifically, thebase wireless communication terminal transmits one management frame tosignal information on each BSS corresponding to a plurality of BSSidentifiers (BSSIDs) included in a multiple BSSID set. The multipleBSSID set is a set of BSSIDs corresponding to each of a plurality ofBSSs classified into one group. When the base wireless communicationterminal uses multiple BSSID sets, since the wireless communicationterminal transmits one management frame and signals information on aplurality of BSSs, it may increase the amount of time that a data framecan occupy a channel. In a specific embodiment, the wirelesscommunication terminal may set the reference BSSID representing themultiple BSSID set to the BSS information indicated by the managementframe, and insert information on a multiple BSSID set into themanagement frame. The information on the multiple BSSID set may includeinformation related to the maximum number of the plurality of BSSIDsincluded in the multiple BSSID set. In this case, the reference BSSIDmay be a BSSID that is a reference when identifying the BSSID includedin the multiple BSSID set. Specifically, the information on the multipleBSSID set may be the multiple BSSID elements in FIG. 11. In this case,the information on the multiple BSSID set may include sub-elements.

The multiple BSSID element may include an Element ID field. The ElementID field is an identifier indicating a multiple BSSID element. Inaddition, the multiple BSSID element may include a Length field. TheLength field is a field indicating the length of multiple BSSIDelements. In addition, the multiple BSSID element may indicate a MaxBSSID indicator field. In this case, the Max BSSID indicator field mayindicate information related to the maximum number of BSSIDs that amultiple BSSID set may include. Specifically, when the value indicatedby the Max BSSID indicator field is n, the maximum number of BSSIDs thata multiple BSSID set may include is 2^(n). In this case, the maximumnumber of BSSIDs is the number including the reference BSSID.

In addition, the multiple BSSID element may include an OptionalSubelements field. The Optional Subelements may include information onthe BSS indicated by the nontransmitted BSSID. The nontransmitted BSSIDindicates the BSSID included in the multiple BSSID set in addition tothe reference BSSID. Specifically, the Optional Subelements field mayinclude a nontransmitted BSSID profile, which is information on the BSSindicated by the nontransmitted BSSID. The Optional Subelements fieldmay include only information on the BSS indicated by some nontransmittedBSSIDs. In this case, the wireless communication terminal may obtaininformation on the BSS indicated by the remaining nontransmitted BSSIDbased on the beacon frame or the probe response frame.

The information on the BSS indicated by the nontransmitted BSSID may bean element to be included in the nontransmitted BSSID Capability elementand the beacon frame body. Specifically, the element that may beincluded in the beacon frame body may be at least one of an SSID, amultiple BSSID-index sub-element, and an FMD Descriptor element. Inaddition, the same information as the BSS information indicated by thereference BSSID among the information on the BSS indicating thenontransmitted BSSID may be omitted. Specifically, at least one of aTimestamp and Beacon Interval field indicated by a Nontransmitted BSSID,a DSSS Parameter Set, an IBSS Parameter Set, Country, Channel SwitchAnnouncement, Extended Channel Switch Announcement, Wide BandwidthChannel Switch, Transmit Power Envelope, Supported Operating Classes,IBSS DFS, ERP Information, HT Capabilities, HT Operation, VHTCapabilities, and a VHT Operation element may be the same as the BSSindicated by the reference BSSID.

In addition, the Optional Subelement field may include a vendor specificelement.

A wireless communication terminal receiving a management frame includinginformation on a multiple BSSID set may obtain information on a multipleBSSID set from a management frame. In this case, the wirelesscommunication terminal may obtain the BSSID included in the multipleBSSID set based on the information on the multiple BSSID set and thereference BSSID. Specifically, the wireless communication terminal canobtain the BSSID included in the multiple BSSID set through thefollowing equation.BSSID(i)=BSSID_A|BSSID_B

In this case, BSSID_A is a BSSID in which (48-n) Most Significant Bit(MSB) values are equal to (48−n) MSB values of the reference BSSID and nLeast Significant Bit (LSB) values are 0. Also, BSSID_B is a BSSID inwhich (48−n) MSB values are 0, and the n LSB values are the remainingvalue (mod) when dividing the sum of n LSBs and i of the reference BSSIDby 2^(n).

In addition, the base wireless communication terminal may signalinformation on multiple BSSID sets using the Operation element. TheOperation element may include a MaxBSSID Indicator field and a Tx BSSIDIndicator field. The MaxBSSID Indicator field may indicate the sameinformation as the MAX BSSID Indicator field of multiple BSSID elements.Therefore, the wireless communication terminal may obtain the BSSID ofthe BSS in which the management frame is transmitted by using theMaxBSSID Indicator field in the same manner as the method of obtainingthe BSSID of the BSS in which the management frame is transmitted usingthe MAX BSSID Indicator field of the multiple BSSID element. The TxBSSID Indicator field indicates whether the BSS to which the managementframe including the Operation element is transmitted corresponds to thenontransmitted BSSID. Specifically, when the Tx BSSID Indicator field is1, the BSS in which the management frame including the Operation elementis transmitted corresponds to the transmitted BSSID. When the Tx BSSIDIndicator field is 0, the BSS in which the management frame includingthe Operation element is transmitted corresponds to the nontransmittedBSSID.

In addition, the wireless communication terminal may signal informationon a capability related to a multiple BSSID set using the Capabilitieselement of the management frame. Specifically, the wirelesscommunication terminal may transmit the Rx Control Frame to MultiBSSfield using the Capabilities element of the management frame. The RxControl Frame to MultiBSS field may indicate whether the frametransmitted from the transmitted BSSID may be received when the wirelesscommunication terminal is associated with the BSS corresponding to thenontransmitted BSSID. Specifically, the Rx Control Frame to MultiBSSfield may indicate whether the control frame transmitted from thetransmitted BSSID may be received when the wireless communicationterminal is associated with the BSS corresponding to the nontransmittedBSSID.

When the BSS including the wireless communication terminal correspondsto the multiple BSSID set, the OFDMA random access operation of thewireless communication terminal is an issue. The reason is because theBSS included in the multiple BSSID set is a formally different BSS butdue to the purpose of using multiple BSSID sets, in the operation of thespecific wireless communication terminal, the BSSs included in themultiple BSSID set may be treated as the identical BSS (Intra-BSS).Also, the reason is because the trigger frame transmitted from thetransmitted BSSID can trigger the uplink transmission of the wirelesscommunication terminal included in the BSS corresponding to thenontransmitted BSSID. Specifically, there is a problem in the operationof the wireless communication terminal relating to the OBO-relatedparameter setting, the OBO procedure initialization, the OBO counterdecrementing operation, and the RU selection for random access.

When the BSS of the wireless communication terminal is included in themultiple BSSID set and the wireless communication terminal is associatedwith the BSS corresponding to the nontransmitted BSSID, the wirelesscommunication terminal may set the OBO-related parameters based on theUORA parameter set transmitted by the transmitted BSSID. When the BSS ofthe wireless communication terminal is included in the multiple BSSIDset and the wireless communication terminal is associated with the BSScorresponding to the nontransmitted BSSID, the wireless communicationterminal may update the OCWmin and OCWmax according to the UORAparameter set transmitted by the transmitted BSSID. In this embodiment,the UORA parameter set may not be included in the nontransmitted BSSIDProfile. In addition, the UORA parameter set may be commonly applied toat least one other BSS included in the multiple BSSID set. Accordingly,when the BSS of the wireless communication terminal is included in themultiple BSSID set and the wireless communication terminal is associatedwith the BSS corresponding to the nontransmitted BSSID, the wirelesscommunication terminal may set the OBO-related parameter according tothe UORA parameter set transmitted by the transmitted BSSID. Inaddition, when the BSS of the wireless communication terminal isincluded in the multiple BSSID set and the wireless communicationterminal is associated with the BSS corresponding to the nontransmittedBSSID, the nontransmitted BSSID Profile subelement corresponding to theBSS associated with the wireless communication terminal may not includethe UORA parameter set element. In such a way, when the nontransmittedBSSID Profile subelement does not include a UORA parameter set element,the wireless communication terminal may set the OBO-related parameteraccording to the UORA parameter set transmitted by the transmittedBSSID.

When the base wireless communication terminal transmits the managementframe in the BSS corresponding to the transmitted BSSID, the basewireless communication terminal can signal the OBO-related parameters tobe used by the wireless communication terminals of the plurality of BSSscorresponding to the multiple BSSID sets using the UORA parameter settransmitted by the transmitted BSSID. Also, when the base wirelesscommunication terminal transmits the management frame in the BSScorresponding to the transmitted BSSID, the base wireless communicationterminal may signal the OBO-related parameters separately from otherBSSs of the multiple BSSID set to the wireless communication terminalsof the BSS corresponding to the nontransmitted BSSID using thenontransmitted BSSID profile subelement. Through these embodiments, thebase wireless communication terminal can efficiently signal theOBO-related parameters to a plurality of wireless communicationterminals included in the BSS corresponding to the multiple BSSID set.

As described above, when the wireless communication terminal is signaledwith information on the OBO-related parameter from the base wirelesscommunication terminal, the wireless communication terminal mayinitialize the OBO procedure. Accordingly, if the BSS of the wirelesscommunication terminal is included in the multiple BSSID set and thewireless communication terminal is associated with the BSS correspondingto the nontransmitted BSSID, when the wireless communication terminalreceives the UORA parameter set transmitted by the transmitted BSSID,the wireless communication terminal may initialize the OBO procedure. Ifthe BSS of the wireless communication terminal is included in themultiple BSSID set and the wireless communication terminal is associatedwith the BSS corresponding to the nontransmitted BSSID, when thewireless communication terminal receives the UORA parameter settransmitted by the transmitted BSSID, the wireless communicationterminal may initiate the OBO procedure. In addition, when the BSS ofthe wireless communication terminal is included in the multiple BSSIDset and the wireless communication terminal is associated with the BSScorresponding to the nontransmitted BSSID, the nontransmitted BSSIDProfile subelement corresponding to the BSS associated with the wirelesscommunication terminal may not include the UORA parameter set element.In this case, the wireless communication terminal may initiate the OBOprocedure. In a specific embodiment, when the wireless communicationterminal initiates the OBO procedure, the wireless communicationterminal may set the OCW to OCWmin and randomly select the OBO counterwithin the OCW.

If the transmitter address TA of the trigger frame is the BSSID of theassociated BSS, the wireless communication terminal may decrement theOBO counter based on the RU indicated by the trigger frame. Therefore,even when the BSS of the wireless communication terminal is included inthe multiple BSSID set, the wireless communication terminal candecrement the OBO counter based on the RU indicated by the trigger framewhen the transmitter address TA of the trigger frame is the BSSID of theBSS associated with the wireless communication terminal. Specifically,when the BSS of the wireless communication terminal is included in themultiple BSSID set and the transmitter address of the trigger frame is atransmitted BSSID, the wireless communication terminal associated withthe BSS having the nontransmitted BSSID may not decrement it based onthe RU indicated by the corresponding trigger frame. In addition, whenthe BSS of the wireless communication terminal is included in themultiple BSSID set and the transmitter address of the trigger frame is anontransmitted BSSID, the wireless communication terminal associatedwith the BSS having the transmitted BSSID may not decrement it based onthe RU indicated by the corresponding trigger frame.

In another specific embodiment, when the transmitter address of thetrigger frame is a transmitted BSSID, the wireless communicationterminal associated with the BSS having a nontransmitted BSSID may allowto decrement the OBO counter based on the trigger frame. However, inthis embodiment, the fairness with the wireless communication terminalassociated with the BSS having a transmitted BSSID may be a problem.Also, when the receiver address of the trigger frame is the BSSIDincluded in the multiple BSSID set, the wireless communication terminalassociated with the BSS included in the multiple BSSID set may allow todecrement the OBO counter based on the trigger frame. In thisembodiment, since the wireless communication terminal associated withthe BSS corresponding to the transmitted BSSID can decrement the OBOcounter based on the trigger frame that can not trigger the wirelesscommunication terminal, the fairness with the random access operation ofthe wireless communication terminals unassociated with the BSScorresponding to the multiple BSSID set may be a problem. Also, only ifthe transmitter address of the trigger frame is a transmitted BSSID andthe trigger frame triggers the transmission to the wirelesscommunication terminal associated with the nontransmitted BSSID, it maybe allowed that the wireless communication terminal associated with theBSSID decrement the OBO counter based on the trigger frame. In order toconfirm whether the trigger frame which transmitted address is thetransmitted BSSID triggers the transmission to the wirelesscommunication terminal associated with the nontransmitted BSSID, thewireless communication terminal may be required to decode the User Infofield. Therefore, this embodiment may increase the complexity of therandom access operation of the wireless communication terminal.

The specific operation of the wireless communication terminal relatingto the OBO-related parameter setting, the OBO procedure initialization,the OBO counter decrementing operation, and the RU selection for randomaccess will be described in detail with reference to FIG. 12.

FIGS. 12 to 13 show a random access operation of a wirelesscommunication terminal associated with multiple BSSID sets according toan embodiment of the present invention.

In the embodiment of FIG. 12, the first station STA1 is associated witha BSS corresponding to a transmitted BSSID of a multiple BSSID set. Thesecond station STA2 is associated with a BSS corresponding to thenontransmitted BSSID of the multiple BSSID set. The first station STA1and the second station STA2 receive the beacon frame transmitted fromthe transmitted BSSID. In this case, the first station STA1 and thesecond station STA2 update OCWmin and OCWmax according to the UORAparameter set element included in the beacon frame. In a specificembodiment, since the UORA parameter set of the beacon frame isadvertised by the transmitted BSSID and is not included in thenontransmitted BSSID profile sub-element, the second station STA2 mayupdate OCWmin and OCWmax according to the UORA parameter set element.

In addition, since the first station STA1 and the second station STA2receive information on the OBO-related parameters from the base wirelesscommunication terminal, the first station STA1 and the second stationSTA2 initialize the OBO procedure. Specifically, the first station STA1and the second station STA2 randomly select an OBO counter within theOCW. The first station STA1 selects 3, and the second station STA2selects 5.

The first station STA1 and the second station STA2 receive a triggerframe having a transmitted BSSID as a transmitter address TA. In thiscase, the trigger frame indicates two RUs allocated for random access.In the embodiment of FIG. 12, it is assumed that a wirelesscommunication terminal associated with a BSS included in a multipleBSSID set can decrement an OBO counter based on a trigger frame having aBSSID included in a multiple BSSID set as a transmitter address.Therefore, the first station STA1 sets the OBO counter to 1 bydecrementing the OBO counter by 2 according to the trigger frame, andthe second station STA2 associated with the BSS corresponding to thenontransmitted BSSID decrements the OBO counter by 2 according to thetrigger frame and sets the OBO counter to 3.

The first station STA1 and the second station STA2 receive a triggerframe having a nontransmitted BSSID as a transmitter address TA. In thiscase, the trigger frame indicates two RUs allocated for random access.The first station STA1 decrements the OBO counter by 2 according to thetrigger frame to set the OBO counter to 0 and randomly selects one ofthe two RUs indicating that the trigger frame is allocated for randomaccess and attempts to perform transmission. The second station STA2associated with the BSS corresponding to the nontransmitted BSSIDdecrements the OBO counter by 2 according to the trigger frame to setthe OBO counter to 1.

If the first station STA1 and the second station STA2 receive a beaconframe that does not include a UORA parameter set element, the firststation STA1 and the second station STA2 maintain the existing OBOprocedure. The first station STA1 and the second station STA2 receivethe beacon frame transmitted from the transmitted BSSID. In this case,the beacon frame includes a UORA parameter set element. Accordingly, thefirst station STA1 and the second station STA2 update OCWmin and OCWmaxaccording to the UORA parameter set element included in the beacon frameand initialize the OBO procedure.

The OBO counter decrementing operation described with reference to FIG.12 can complicate the random access operation of the wirelesscommunication terminal as described above, and may cause a problem ofthe fairness with other wireless communication terminals. Therefore, asshown in FIG. 13, even when the BSS of the wireless communicationterminal is included in the multiple BSSID set, the wirelesscommunication terminal can decrement the OBO counter based on the RUindicated by the trigger frame when the transmitter address TA of thetrigger frame is the BSSID of the BSS associated with the wirelesscommunication terminal.

In the embodiment of FIG. 13, the descriptions on the same operation andsituation as those of the embodiment of FIG. 12 will be omitted. Thefirst station STA1 and the second station STA2 receive a trigger framehaving a transmitted BSSID as a transmitter address TA. In this case,the trigger frame indicates two RUs allocated for random access. Thefirst station STA1 associated with the BSS corresponding to thetransmitted BSSID decrements the OBO counter by 2 according to thetrigger frame to set the OBO counter to 1. Since the second station STA2is associated with the BSS corresponding to the nontransmitted BSSID,the second station STA2 maintains the OBO counter as 5.

In addition, the first station STA1 and the second station STA2 receivea trigger frame having a nontransmitted BSSID as a transmitter addressTA. In this case, the trigger frame indicates two RUs allocated forrandom access. Since the first station STA1 is associated with the BSScorresponding to the transmitted BSSID, the first station STA1 maintainsthe OBO counter as 1. The second station STA2 associated with the BSScorresponding to the nontransmitted BSSID decrements the OBO counter by2 to set the OBO counter to 3.

Even if the trigger frame triggers the random access, when thecapability of the wireless communication terminal does not support theuplink transmission condition indicated by the trigger frame, even whenthe OBO counter reaches 0, the wireless communication terminal can notperform random access. For example, when the wireless communicationterminal does not support transmission of the frequency bandwidth of theRU which is indicated as an RU allocated for the random access, thecorresponding wireless communication terminal can not perform randomaccess to the corresponding RU. Therefore, a random access operationconsidering the capability of the wireless communication terminal isrequired.

When the wireless communication terminal receives the trigger frame, thewireless communication terminal can decrement the OBO counter accordingto the capability of the wireless communication terminal. Specifically,when the wireless communication terminal receives the trigger frame, thewireless communication terminal may decrement the OBO counter based onthe RU allocated for the random access and the capability of thewireless communication terminal. In a specific embodiment, the wirelesscommunication terminal may decrement the OBO counter by the number ofRUs, through which the wireless communication terminal is capable oftransmitting the TB PPDU according to the capability of the wirelesscommunication terminal, among the RUs allocated for the random access.As described above, an RU allocated for random access may be indicatedby a trigger frame. In addition, the wireless communication terminal maydetermine whether the TB PPDU can be transmitted through the RU based onthe transmission condition indicated by the trigger frame.

Further, when the OBO counter reaches 0, the wireless communicationterminal may select the RU according to the capability of the wirelesscommunication terminal. In a specific embodiment, when the OBO counterreaches 0, the wireless communication terminal may randomly select anyone of the RUs, which are allocated for the random access and in whichthe wireless communication terminal is capable of transmitting the TBPPDU according to the capability of the wireless communication terminal.

When the OBO counter reaches 0, the wireless communication terminal maydefer the random access and maintain the OBO counter. Specifically, whendata corresponding to the response length indicated by the trigger frameis not buffered in the wireless communication terminal, the wirelesscommunication terminal may defer the random access and maintain the OBOcounter as 0. In this case, the wireless communication terminal mayperform random access in response to the next trigger frame thattriggers the random access. In addition, if there is no RU through whichthe wireless communication terminal is capable of transmitting the TBPPDU according to the capability of the wireless communication terminalamong the RUs allocated for the random access, the wirelesscommunication terminal may maintain the OBO counter as 0. In this case,the wireless communication terminal may perform random access inresponse to the next trigger frame that triggers the random access.

Also, the capabilities of the wireless communication terminal mayinclude the capability of the wireless communication terminal related toat least one of the bandwidth through which transmission is supported,Modulation & Coding Scheme (MCS), Dual Carrier Modulation (DCM), thenumber of spatial streams, the length of Guard Interval (GI), the LongTraining Field (LTF) type, the space-time block coding (STBC),transmission power, and length of the padding field. The length of thepadding field may indicate the length of the padding field included inthe TB PPDU. The specific operation of the wireless communicationterminal will be described with reference to FIG. 14 to FIG. 21.

FIG. 14 shows types of RUs and subcarrier indexes that may be used whentransmitting a PPDU which bandwidth is 20 Mhz according to an embodimentof the present invention. FIG. 15 shows types of RUs and subcarrierindexes that may be used when transmitting a PPDU which bandwidth is 40Mhz according to an embodiment of the present invention. FIG. 16 showstypes of RUs and subcarrier indexes that may be used when transmitting aPPDU which bandwidth is 80 Mhz bandwidth according to an embodiment ofthe present invention.

As described above, the RU may indicate that a plurality of subcarriersthat may be useable for uplink and downlink transmission are groupedaccording to the size of the frequency band.

The wireless communication terminal according to an embodiment of thepresent invention can perform uplink transmission or downlinktransmission using at least one of an RU (26-tone RU) using 26subcarriers, an RU (52-tone RU) using 52 subcarriers, an RU (106-toneRU) using 106 subcarriers, an RU (242-tone RU) using 242 subcarriers, anRU (484-tone RU) using 484 subcarriers, an RU (996-tone RU) using 996subcarriers, and an RU (2*996-tone RU) using 1992 subcarriers.Specifically, the wireless communication terminal can transmit the HE MUPPDU or the HE trigger-based PPDU through the OFDMA using the designatedRU. In this case, when the frequency bandwidth of the PPDU is any one of20 Mhz, 40 Mhz, 80 Mhz, 160 MHz, and 80+80 Mhz, the wirelesscommunication terminal can transmit the PPDU using any one of the26-tone RU, the 52-tone RU, the 106-tone RU, and the 242-tone RU. Inaddition, when the frequency bandwidth of the PPDU is any one of 40 Mhz,80 Mhz, 160 MHz, and 80+80 Mhz, the wireless communication terminal cantransmit the PPDU using the 484-tone RU. In addition, when the frequencybandwidth of the PPDU is any one of 80 Mhz, 160 MHz, and 80+80 Mhz, thewireless communication terminal can use the 996-tone RU. In addition,when the frequency bandwidth of the PPDU is any one of 160 MHz and 80+80MHz, the wireless communication terminal can transmit the PPDU using the2*996-tone RU.

Also, the wireless communication terminal can transmit the HE SingleUser (SU) PPDU using the designated RU. In this case, if the frequencybandwidth of the HE SU PPDU is 20 Mhz, the wireless communicationterminal can transmit the HE SU PPDU using the 242-tone RU. Also, if thefrequency bandwidth of the HE SU PPDU is 40 Mhz, the wirelesscommunication terminal can transmit the HE SU PPDU using the 484-toneRU. Also, if the frequency bandwidth of the HE SU PPDU is 80 Mhz, thewireless communication terminal can transmit the HE SU PPDU using the996-tone RU. Also, if the frequency bandwidth of the HE SU PPDU is 160MHz or 80+80 Mhz, the wireless communication terminal can transmit theHE SU PPDU using the 2*996-tone RU.

The 26-tone RU may include 24 subcarriers for transmitting data and 2subcarriers for transmitting pilot signals. The specific position of the26-tone RU may be the same as those as shown in FIGS. 14, 15, and 16.When the frequency bandwidth of the PPDU transmitted by the wirelesscommunication terminal is a 160 MHz or 80+80 Mhz PPDU, the 26-tone RUtransmitted through each 80 Mhz frequency band may be the same as thatshown in FIG. 15. The 52-tone RU may include 48 subcarriers fortransmitting data and 4 subcarriers for transmitting pilot signals. Thespecific position of the 52-tone RU may be the same as those shown inFIGS. 14, 15, and 16. When the frequency bandwidth of the PPDUtransmitted by the wireless communication terminal is a 160 MHz or 80+80Mhz PPDU, the 52-tone RU transmitted through each 80 Mhz frequency bandmay be the same as that shown in FIG. 15.

The 106-tone RU may include 102 subcarriers for transmitting data and 4subcarriers for transmitting pilot signals. The specific position of the106-tone RU may be the same as those shown in FIGS. 14, 15, and 16. Whenthe frequency bandwidth of the PPDU transmitted by the wirelesscommunication terminal uses a 160 MHz or 80+80 Mhz PPDU, the 106-tone RUtransmitted through each 80 Mhz frequency band may be the same as thatshown in FIG. 15. The 242-tone RU may include 234 subcarriers fortransmitting data and 8 subcarriers for transmitting pilot signals. Thespecific position of the 242-tone RU may be the same as those shown inFIGS. 14, 15, and 16. When the frequency bandwidth of the PPDUtransmitted by the wireless communication terminal is a 160 MHz or 80+80Mhz PPDU, the 242-tone RU transmitted through each 80 Mhz frequency bandmay be the same as that shown in FIG. 15.

The 484-tone RU may include 468 subcarriers for transmitting data and 16subcarriers for transmitting pilot signals. The specific position of the484-tone RU may be the same as those shown in FIGS. 15 and 16. When thefrequency bandwidth of the PPDU transmitted by the wirelesscommunication terminal is a 160 MHz or 80+80 Mhz PPDU, the 484-tone RUtransmitted through each 80 Mhz frequency band may be the same as thatshown in FIG. 15. The 996-tone RU may include 980 subcarriers fortransmitting data and 16 subcarriers for transmitting pilot signals. Thespecific position of the 996-tone RU may be the same as that shown inFIG. 15. When the frequency bandwidth of the PPDU transmitted by thewireless communication terminal is a 160 MHz or 80+80 Mhz PPDU, the996-tone RU transmitted through each 80 Mhz frequency band may be thesame as that shown in FIG. 15. When a wireless communication terminaltransmits a PPDU having a bandwidth of 160 MHz or 80+80 Mhz, thesubcarriers included in the 996-tone RU are located at [−1012: −515,−509: −12] and [12: 509, 515: 1012]. In this case, [x: y] represents thesubcarrier indices x to y. Therefore, even when using the 2*996-tone RU,the wireless communication terminal uses the subcarriers located in thesubcarrier indexes of [−1012: −515, −509: −12] and [12: 509, 515: 1012].

If the wireless communication terminal transmits an HE MU PPDU or HEtrigger-based PPDU having a frequency bandwidth of 20 Mhz and the PPDUincludes two or more RUs, the wireless communication terminal maytransmit seven Direct Current (DC) subcarriers at [−3: 3]. When awireless communication terminal transmits a HE SU PPDU having afrequency bandwidth of 20 Mhz using a 242-tone RU, the wirelesscommunication terminal may transmit three DC subcarriers at [−1: 1].When a wireless communication terminal transmits a HE SU PPDU having afrequency bandwidth of 40 MHz using a 484-tone RU, the wirelesscommunication terminal may transmit five DC subcarriers at [−2: 2]. Ifthe wireless communication terminal transmits an HE MU PPDU or HEtrigger-based PPDU having a frequency bandwidth of 80 Mhz and the PPDUincludes two or more RUs, the wireless communication terminal maytransmit seven DC subcarriers at [−3: 3]. When a wireless communicationterminal transmits a HE SU PPDU having a frequency bandwidth of 80 Mhzusing a 996-tone RU, the wireless communication terminal may transmitfive DC subcarriers at [−2: 2]. When a wireless communication terminaltransmits a PPDU having a bandwidth of 160 MHz or 80+80 MHz, thewireless communication terminal may transmit the DC subcarrier to thesame position as that in the case of transmitting the HE SU PPDU havingthe frequency bandwidth of 80 Mhz in each 80 Mhz band using the 996-toneRU.

When a wireless communication terminal transmits a PPDU having a 20 Mhzfrequency bandwidth, the wireless communication terminal may transmiteleven guard subcarriers to [−128: −123] and [123: 127]. When a wirelesscommunication terminal transmits a PPDU having a 40 Mhz frequencybandwidth, the wireless communication terminal may transmit 23 guardsubcarriers to [−256: −245] and [245: 255]. When a wirelesscommunication terminal transmits a PPDU having an 80 Mhz frequencybandwidth, the wireless communication terminal can transmit 23 guardsubcarriers to [−512: −501] and [501: 511]. When a wirelesscommunication terminal transmits a PPDU having a 160 MHz or 80+80 Mhzfrequency bandwidth, the wireless communication terminal may transmitthe guard subcarriers used in transmitting the PPDU having the 80 Mhzfrequency bandwidth to both ends.

FIG. 17 shows an encoding value used for indicating an RU in an RUAllocation subfield of a trigger frame according to an embodiment of thepresent invention.

The RU Allocation subfield indicates the RU to be used for transmissionby the wireless communication terminal triggered by the trigger frame.The RU Allocation subfield may be an 8-bit field. In this case, one bitof the RU Allocation subfield, for example, B12, may indicate whetherthe RU indicated by the RU Allocation subfield is in a primary 80 Mhzchannel or a non-primary 80 Mhz channel. The primary channel representsthe frequency band that is the basis of the frequency band extension.Also, the primary channel may refer to a contiguous frequency band thatincludes a frequency band having a 20 Mhz frequency bandwidth, which isthe basis of frequency band extension. Also, when the RU has a frequencybandwidth of 80 Mhz or less, 7 bits of the RU Allocation subfield, e.g.,B19-B13, indicate which RU is indicated in 80 Mhz. Also, when the RU hasa frequency bandwidth equal to or wider than 80 Mhz, the 7 bits of theRU Allocation subfield, e.g., B19-B13, indicate which RU is indicated ina frequency bandwidth equal to or wider than 80 Mhz. The specific valueof the RU Allocation field may be the same as that in FIG. 17.

Specifically, in the case of a PPDU having a frequency bandwidth of 20Mhz, 40 MHz or 80 Mhz, B12 may be set to 0. In addition, in the case ofthe 2*996-tone RU, B12 may be set to 1. Moreover, B19-B13 may also beset as follows.

-   -   When the wireless communication terminal transmits a PPDU having        a frequency bandwidth of 20 Mhz, the wireless communication        terminal may designate the RU index of FIG. 14 in B19-B13        according to ascending order. When the value of B19-B13 is        0000000, the RU Allocation subfield may indicate the 26-tone RU        1. When the value of B19-B13 is 0001000, the RU Allocation        subfield may indicate the 26-tone RU 9. The value of B19-B13 may        not use 0001001 to 0100100. When the value of B19-B13 is        0100101, the RU Allocation subfield may indicate the 52-tone RU        1. When the value of B19-B13 is 0101000, the RU Allocation        subfield may indicate the 52-tone RU 4. The value of B19-B13 may        not use 0101001 to 0110100. When the value of B19-B13 is        0110101, the RU Allocation subfield may indicate the 106-tone RU        1. When the value of B19-B13 is 0110110, the RU Allocation        subfield may indicate the 106-tone RU 2. The value of B19-B13        may not use 0110111 to 0111100. When the value of B19-B13 is        0111101, the RU Allocation subfield may indicate the 242-tone RU        1. The value of B19-B13 may not use 0111110 to 1000000.    -   When the wireless communication terminal transmits a PPDU having        a frequency bandwidth of 40 Mhz, the wireless communication        terminal may designate the RU index of FIG. 15 in B19-B13        according to ascending order. When the value of B19-B13 is        0000000, the RU Allocation subfield may indicate 26-tone RU 1.        When the value of B19-B13 is 0010001, the RU Allocation subfield        may indicate the 26-tone RU 18. The value of B19-B13 may not use        0010010 to 0100100. When the value of B19-B13 is 0100101, the RU        Allocation subfield may indicate the 52-tone RU 1. When the        value of B19-B13 is 0101100, the RU Allocation subfield may        indicate the 52-tone RU 8. The value of B19-B13 may not use        0101101 to 0110100. The value of B19-B13 may be designated for        the 106-tone, 242-tone and 484-tone RUs according to the rules        such as the 26-tone RU and the 52-tone RU.    -   When the wireless communication terminal transmits a PPDU having        a frequency bandwidth of 80 Mhz, 160 MHz, and 80+80 Mhz, the        wireless communication terminal may designate the RU index of        FIG. 12 in B19-B13 according to ascending order. When the value        of B19-B13 is 0000000, the RU Allocation subfield may indicate        the 26-tone RU 1. When the value of B19-B13 is 0100100, the RU        Allocation subfield may indicate the 26-tone RU 37. When the        value of B19-B13 is 0100101, the RU Allocation subfield may        indicate the 52-tone RU 1. If the value of B19-B13 is 0110100,        the value of the RU Allocation subfield may indicate the 52-tone        RU 16. The value of B19-B13 may be designated for the 106-tone,        242-tone, 484-tone, and 996-tone RUs according to the rules such        as the 26-tone RU and the 52-tone RU. When the wireless        communication terminal transmits a 160 MHz or 80+80 Mhz PPDU and        the value of B19-B13 is 1000100, the RU Allocation subfield may        indicate a 2*996-tone RU.

The wireless communication terminal can support transmission andreception of PPDUs which frequency bandwidth is equal to or narrowerthan a certain size. For example, the wireless communication terminalmay only support transmission and reception of PPDUs which bandwidth is20 Mhz. In addition, the wireless communication terminal may supporttransmission and reception of PPDUs which frequency bandwidth is 80 MHzor less. In such a way, when the wireless communication terminal onlysupports transmission and reception of PPDUs which frequency bandwidthis equal to or narrower than a certain size, the wireless communicationterminal may decrement the OBO counter based on the number of RUsincluded in the frequency bandwidth which is equal to or narrower than acertain size among the RUs allocated for the random access. In thiscase, the RU allocated for the random access may be indicated by thetrigger frame. Further, the wireless communication terminal decrementsthe OBO counter when receiving the trigger frame. Specifically, when thewireless communication terminal only supports transmission and receptionof PPDUs which frequency bandwidth is equal to or narrower than acertain size, the wireless communication terminal may decrement the OBOcounter based on the number of RUs included in the primary channel whichfrequency bandwidth is equal to or narrower than a certain size amongthe RUs allocated for the random access. The wireless communicationterminal may not support the non-primary channel because it is difficultto switch the channel within a certain time. In this case, thenon-primary channel may refer to a channel other than the primarychannel. For example, when the wireless communication terminal onlysupports transmission and reception of PPDUs which frequency bandwidthis equal to or narrower than 20 Mhz, the wireless communication terminalmay decrement the OBO counter based on the number of RUs in which theB19-B13 value of the RU Allocation subfield is 0000000 to 0001000 or0100101 to 0101000 or 0110101 to 0110110 or 0111101 among the RUsallocated for random access. In another specific embodiment, when thewireless communication terminal only supports transmission and receptionof PPDUs having a frequency bandwidth which is equal to or narrower thana certain size, the wireless communication terminal may decrement theOBO counter based on the number of RUs included in the frequencybandwidth which is equal to or narrower than a certain size among theRUs allocated for the random access irrespective of whether the RU isincluded in the primary channel. For example, when the wirelesscommunication terminal only supports PPDU transmission and receptionwith a frequency bandwidth equal to or narrower than 20 Mhz or less, thewireless communication terminal may decrement the OBO counter based onthe number of RUs in which the B19-B13 value of the RU Allocationsubfield is less than or equal to 1000000 among the RUs allocated forrandom access.

In addition, when the OBO counter reaches 0 and the wirelesscommunication terminal only supports transmission and reception of PPDUswhich frequency bandwidth is equal to or narrower than a certain size,the wireless communication terminal may randomly select any one of theRUs allocated for the random access and included in the frequencybandwidth which is equal to or narrower than a certain size. In thiscase, the wireless communication terminal may attempt transmissionthrough the selected RU. The RU allocated for the random access may beindicated by the trigger frame as described above. When there is nofrequency bandwidth equal to or narrower than a certain size among theRUs allocated for the random access, the wireless communication terminalmay maintain the OBO counter without attempting transmission. In thiscase, the wireless communication terminal may attempt random access inresponse to the next trigger frame transmitted. In this embodiment, whenthe wireless communication terminal decrements the OBO counter, thewireless communication terminal may not consider the capability of thewireless communication terminal. Specifically, when the wirelesscommunication terminal decrement the OBO counter regardless of whetherthe RU is included in a frequency bandwidth of a certain size or less,the wireless communication terminal may randomly select any one of theRUs allocated for the random access and included in the frequencybandwidth of a certain size or less when the OBO counter reaches 0.

Also, in a specific embodiment, the wireless communication terminal mayrandomly select any one of the RUs allocated for the random access andthe RUs included in the primary channel which bandwidth is equal to ornarrower than a certain size. The wireless communication terminal maynot support the non-primary channel because it is difficult to switchthe channel within a certain time. For example, when the wirelesscommunication terminal only supports transmission and reception of PPDUswhich frequency bandwidth is equal to or narrower than 20 Mhz, thewireless communication terminal can arbitrarily select any one of theRUs allocated for the random access and the RUs in which the B19-B13value of the RU Allocation subfield corresponding to the correspondingRU is 0000000 to 0001000 or 0100101 to 0101000 or 0110101 to 0110110 or0111101. In another specific embodiment, when the wireless communicationterminal only supports transmission and reception of PPDUs whichfrequency bandwidth is equal to or narrower than a certain size, thewireless communication terminal may randomly select any one of the RUsallocated for the random access irrespective of whether the RU isincluded in the primary channel and included in the frequency bandwidthof a certain size or less. For example, when the wireless communicationterminal only supports PPDU transmission and reception with a frequencybandwidth equal to or narrower than 20 Mhz, the wireless communicationterminal can arbitrarily select any one of the RUs allocated for therandom access, in which the B19-B13 value of the RU Allocation subfieldcorresponding to the corresponding RU is 1000000 or less.

FIGS. 18 to 19 show operations in which a wireless communicationterminal supporting only a PPDU which bandwidth is 20 Mhz performsrandom access according to an embodiment of the present invention.

In the embodiments of FIGS. 18 to 21, the wireless communicationterminal decrement the OBO counter based on the frequency bandwidth thatthe wireless communication terminal supports. In the embodiment of FIGS.18 and 20, when the RU allocated for the random access is included inthe primary channel which frequency bandwidth is equal to or narrowerthan a certain size, the wireless communication terminal decrements theOBO counter based on the corresponding RU.

In the embodiment of FIG. 18, the first station STA1 only supports afrequency band equal to or narrower than 20 Mhz. The second station STA2supports a frequency band equal to or wider than 20 Mhz. The firststation STA1 and the second station STA2 receive a beacon frame from thefirst AP AP1. The first station STA1 and the second station STA2 obtainthe UORA parameter set element from the beacon frame and initialize theOBO procedure. Specifically, the first station STA1 sets OCWmin andOCWmax according to the UORA parameter set element, and initializes theOCW. The first station STA1 randomly selects 10 in the OCW and sets theOBO counter to 10. In addition, the second station STA2 sets OCWmin andOCWmax according to the UORA parameter set element, and initializes theOCW. The second station STA2 arbitrarily selects 12 in the OCW and setsthe OBO counter to 12.

The first station STA1 and the second station STA2 receive a triggerframe from the first AP AP1. In this case, the trigger frame indicatestwo RUs with RUs allocated for random access. One RU is included in theprimary channel with a 20 Mhz frequency bandwidth and the other RU isnot included in the primary channel with a 20 Mhz frequency bandwidth.Since the first station STA1 only supports a frequency bandwidth equalto or narrower than 20 Mhz, the first station STA1 decrements the OBOcounter by 1 and sets the OBO counter to 9. Since the second stationSTA2 also supports a frequency bandwidth equal to or wider than 20 Mhz,the second station STA2 decrements the OBO counter by 2 and sets the OBOcounter to 10.

In the embodiment of FIG. 19, the first station STA1 supports only afrequency band equal to or narrower than 20 MHz, and the second stationSTA2 supports a frequency band equal to or wider than 20 Mhz, as in theembodiment of FIG. 18. Description of operations of the first stationSTA1 and the second station STA2, which are the same as those in theembodiment of FIG. 18, will be omitted.

The first station STA1 and the second station STA2 receive a triggerframe from the first AP AP1. In this case, the trigger frame indicatestwo RUs with RUs allocated for random access. One RU has a frequencybandwidth equal to or narrower than 20 Mhz, and the other RU has afrequency bandwidth wider than 20 Mhz. Since the first station STA1 onlysupports a frequency bandwidth equal to or narrower than 20 Mhz, thefirst station STA1 decrements the OBO counter by 1 and sets the OBOcounter to 9. Since the second station STA2 also supports a frequencybandwidth equal to or wider than 20 Mhz, the second station STA2decrements the OBO counter by 2 and sets the OBO counter to 10.

FIGS. 20 to 21 show operations in which a wireless communicationterminal supporting only a PPDU which bandwidth is equal to or narrowerthan 80 Mhz performs random access according to an embodiment of thepresent invention.

In the embodiment of FIG. 20, the first station STA1 supports only afrequency band equal to or narrower than 80 Mhz, and the second stationSTA2 supports a frequency band (160 MHz, 80+80 Mhz) equal to or widerthan 80 Mhz. Description of operations of the first station STA1 and thesecond station STA2, which are the same as those in the embodiment ofFIGS. 18 to 19, will be omitted.

The first station STA1 and the second station STA2 receive a triggerframe from the first AP AP1. In this case, the trigger frame indicatestwo RUs with RUs allocated for random access. One RU is included in theprimary channel with an 80 Mhz frequency bandwidth and the other RU isnot included in the primary channel with an 80 Mhz frequency bandwidth.Since the first station STA1 only supports a frequency bandwidth equalto or narrower than 80 Mhz, the first station STA1 decrements the OBOcounter by 1 and sets the OBO counter to 9. Since the second stationSTA2 also supports a frequency bandwidth equal to or wider than 80 Mhz,the second station STA2 decrements the OBO counter by 2 and sets the OBOcounter to 10.

In the embodiment of FIG. 21, the first station STA1 supports only afrequency band of 80 Mhz or less, and the second station STA2 supports afrequency band (160 MHz, 80+80 Mhz) equal to or wider than 80 Mhz as inthe embodiment of FIG. 20. Description of operations of the firststation STA1 and the second station STA2, which are the same as those inthe embodiment of FIGS. 18 to 20, will be omitted.

The first station STA1 and the second station STA2 receive a triggerframe from the first AP AP1. In this case, the trigger frame indicatestwo RUs with RUs allocated for random access. One RU has a frequencybandwidth equal to or narrower than 80 Mhz, and the other RU has afrequency bandwidth wider than 80 Mhz. Since the first station STA1 onlysupports a frequency bandwidth equal to or narrower than 80 Mhz, thefirst station STA1 decrements the OBO counter by 1 and sets the OBOcounter to 9. Since the second station STA2 also supports a frequencybandwidth equal to or wider than 20 Mhz, the second station STA2decrements the OBO counter by 2 and sets the OBO counter to 10.

In the above-described random access operation of the wirelesscommunication terminal, the wireless communication terminal receives theinformation on the OBO-related parameters from the base wirelesscommunication terminal associated with the wireless communicationterminal and sets the OBO-related parameters according to the receivedinformation. Specifically, the UORA parameter set element is receivedfrom the base wireless communication terminal associated with thewireless communication terminal and the OBO-related parameter is setbased on the UORA parameter set element. A wireless communicationterminal unassociated with a base wireless communication terminal canperform random access based on a trigger frame transmitted by the basewireless communication terminal. In such a case, a method of setting theOBO-related parameters and a method of initializing an OBO procedure byan unassociated wireless communication terminal become problematic. Thiswill be described in detail with reference to FIGS. 22 to 25. If thereis no additional description in this specification, an unassociatedwireless communication terminal may represent a wireless communicationterminal unassociated with any base wireless communication terminal.

FIG. 22 shows the random access operation of an unassociated wirelesscommunication terminal according to an embodiment of the presentinvention.

When the wireless communication terminal receives the trigger frametriggering the random access of the wireless communication terminal fromthe base wireless communication terminal unassociated with the wirelesscommunication terminal, the wireless communication terminal may startthe OBO procedure based on the information on the OBO-related parameterstransmitted by the corresponding base wireless communication terminal.Specifically, the wireless communication terminal may receive the UORAparameter set element from the wireless communication terminalunassociated with the base wireless communication terminal. In thiscase, when the wireless communication terminal receives the triggerframe triggering the random access of the wireless communicationterminal from the corresponding base wireless communication terminal,the wireless communication terminal may set the OCWmin and OCWmaxaccording to the UORA parameter set element and start the OBO procedure.

When a wireless communication terminal receives a trigger frametriggering a random access of a wireless communication terminal from awireless communication terminal different from the base wirelesscommunication terminal transmitting the UORA parameter set element, thewireless communication terminal may not perform the OBO-relatedprocedure according to the received UORA parameter set element.Specifically, when a wireless communication terminal receives a triggerframe triggering a random access of a wireless communication terminalfrom a wireless communication terminal different from the base wirelesscommunication terminal transmitting the UORA parameter set element, thewireless communication terminal may not decrement the OBO counter basedon the trigger frame. For this, the wireless communication terminal maycompare the identifier of the base wireless communication terminaltransmitting the UORA parameter set element with the identifier of thebase wireless communication terminal transmitting the trigger frame. Inthis case, the identifier of the base wireless communication terminalmay be a MAC address or a BSSID. In the above-described embodiments, thetrigger frame for triggering the random access may be a trigger framefor triggering the random access of the unassociated wirelesscommunication terminal.

In addition, when a wireless communication terminal receives a new UORAparameter set element from a wireless communication terminal differentfrom a base wireless communication terminal transmitting a UORAparameter set element, the wireless communication terminal may notinitialize the OBO procedure based on the newly received UORA parameterset element. In this case, the initialization of the OBO procedureincludes at least one of OBO counter initialization and OCWinitialization. In addition, when a wireless communication terminalreceives a new UORA parameter set element from a wireless communicationterminal different from a base wireless communication terminaltransmitting a UORA parameter set element, the wireless communicationterminal may not set the OBO-related parameter based on the newlyreceived UORA parameter set element. In this case, setting of theOBO-related parameter may include at least one of OCWmin setting andOCWmax setting. For this, the wireless communication terminal maycompare the identifier of the base wireless communication terminaltransmitting the UORA parameter set element with the identifier of thebase wireless communication terminal transmitting a new UORA parameterset element. In this case, the identifier of the base wirelesscommunication terminal may be a MAC address or a BSSID. Through thisembodiment, it is possible to prevent the unassociated wirelesscommunication terminal from initiating the OBO procedure continuously orperforming random access while damaging the fairness with the otherwireless communication terminals.

In the embodiment of FIG. 22, the first station STA1 is a wirelesscommunication terminal unassociated with any base wireless communicationterminal. The first station STA1 receives the beacon frame from thefirst AP AP1 and obtains the UORA parameter set element from thereceived beacon frame. The first station STA1 sets an OBO-relatedparameter according to the obtained UORA parameter set element, andinitializes the OBO procedure. Specifically, the first station STA1 setsOCWmin and OCWmax according to the obtained UORA parameter set element,and selects an arbitrary integer in the OCW. In this case, thearbitrarily selected integer is 10, and the first station STA1 sets theOBO counter to 10.

The first station STA1 receives a trigger frame indicating two RUsallocated for random access from the first AP AP1. In this case, thefirst station STA1 decrements the OBO counter by 2 and sets the OBOcounter to 8.

The first station STA1 receives a trigger frame indicating two RUsallocated for random access from the second AP AP2. Since the first APAP1 and the second AP AP2 transmitting the UORA parameter set elementused to set the OBO-related parameters have different identifiers, thefirst station STA1 maintains the OBO counter as it is.

The first station STA1 receives a beacon frame from the second AP AP2,and the received beacon frame includes a UORA parameter set element.Since the first AP AP1 and the second AP AP2 transmitting the UORAparameter set element used to set the OBO-related parameters havedifferent identifiers, the first station STA1 does not update theOBO-related parameters.

The first station STA1 receives the beacon frame from the first AP AP1and obtains the UORA parameter set element from the received beaconframe. Since the first station STA1 receives the UORA parameter setelement again from the first AP AP1 transmitting the UORA parameter setelement used for setting the OBO related parameter, the first stationSTA1 updates the OBO-related parameter according to the newly receivedUORA parameter set element.

According to the embodiment described with reference to FIG. 22, theunassociated wireless communication terminal may not participate in therandom access triggered by the base wireless communication terminalother than the base wireless communication terminal that received thefirst UORA parameter set element. Therefore, a method for solving thisis needed.

FIG. 23 shows the random access operation of an associated wirelesscommunication terminal according to an embodiment of the presentinvention.

When the unassociated wireless communication terminal performs the OBOprocedure for the first base wireless communication terminal andperforms the OBO procedure for the second base wireless communicationterminal, the unassociated wireless communication terminal may initiatethe OBO procedure. Specifically, the unassociated wireless communicationterminal may maintain the OBO-related parameters and the OBO procedurefor each base wireless communication terminal. In a specific embodiment,the unassociated wireless communication terminal may set an OBO-relatedparameter for each base wireless communication terminal. Specifically,the unassociated wireless communication terminal may set the OBO-relatedparameters for each base wireless communication terminal based on theinformation on the OBO-related parameters received from each basewireless communication terminal. In a specific embodiment, when thewireless communication terminal receives the UORA parameter set elementfrom any one of the base wireless communication terminals, the wirelesscommunication terminal may update the OBO-related parameters for thecorresponding UORA parameter set element. In this case, the OBO-relatedparameter may be at least one of OCWmin and OCWmax.

Also, the unassociated wireless communication terminal may initializethe OBO procedure for each base wireless communication terminal.Specifically, the unassociated wireless communication terminal maymaintain the OBO counter for each base wireless communication terminal.In a specific embodiment, when an unassociated wireless communicationterminal receives a trigger frame triggering a random access from anyone base wireless communication terminal, the unassociated wirelesscommunication terminal can decrement the OBO counter for the basewireless communication terminal based on the number of RUs for randomaccess indicated by the corresponding trigger frame.

In the embodiment of FIG. 23, the first station STA1 is a wirelesscommunication terminal unassociated with any base wireless communicationterminal. The first station STA1 receives the beacon frame from thefirst AP AP1 and obtains the UORA parameter set element from thereceived beacon frame. The first station STA1 sets an OBO-relatedparameter Set 1 for the first AP AP1 according to the obtained UORAparameter set element, and initializes the OBO procedure. Specifically,the first station STA1 sets OCWmin and OCWmax for the first AP AP1according to the obtained UORA parameter set element, and selects arandom integer in the OCW for the first AP AP1. In this case, therandomly selected integer is 10, and the first station STA1 sets the OBOcounter for the first AP AP1 to 10.

The first station STA1 receives a trigger frame indicating two RUsallocated for random access from the first AP AP1. In this case, thefirst station STA1 decrements the OBO counter for the first AP AP1 by 2and sets the OBO counter for the first AP AP1 to 8.

The first station STA1 receives the beacon frame from the second AP AP2and obtains the UORA parameter set element from the received beaconframe. Since the first AP AP1 and the second AP AP2 transmitting theUORA parameter set element used to set the OBO-related parameters havedifferent identifiers, the first station STA1 sets the OBO-relatedparameter Set 2 for the second AP AP2 according to the obtained UORAparameter set element and initializes the OBO procedure for the secondAP AP2. Specifically, the first station STA1 sets OCWmin and OCWmax forthe second AP AP2 according to the obtained UORA parameter set element,and selects a random integer in the OCW for the second AP AP2. In thiscase, the randomly selected integer is 12, and the first station STA1sets the OBO counter for the second AP AP2 to 12. In this case, thefirst station STA1 does not update the OBO-related parameters for thefirst AP AP1 and does not initialize the OBO procedure.

The first station STA1 receives a trigger frame indicating two RUsallocated for random access from the second AP AP2. In this case, thefirst station STA1 decrements the OBO counter for the second AP AP2 by 2and sets the OBO counter for the second AP AP2 to 10. In this case, thefirst station STA1 maintains the OBO counter for the first AP AP1 as 8as it is.

According to the embodiment of FIGS. 22 to 23, when the wirelesscommunication terminal does not receive information on the OBO-relatedparameters from the base wireless communication terminal, the wirelesscommunication terminal can not participate in the random access.Therefore, operations of the wireless communication terminal arenecessary to solve such a problem.

FIG. 24 shows the random access operation of an associated wirelesscommunication terminal according to an embodiment of the presentinvention.

The unassociated wireless communication terminal may perform randomaccess using default values predefined for each OBO-related parameter.Specifically, the unassociated wireless communication terminal may set apredetermined value as a default value of OCWmin in OCWmin. Further, theunassociated wireless communication terminal may set a predeterminedvalue as a default value of OCWmax in OCWmax. In this case, the valuepredetermined as the default value of OCWmin may not be a valuedesignated by the base wireless communication terminal. In addition, thevalue predetermined as the default value of OCWmax may not be a valuedesignated by the base wireless communication terminal. Specifically,when the unassociated wireless communication terminal does not receiveinformation on the OBO-related parameters from the base wirelesscommunication terminal, the unassociated wireless communication terminalmay use a predetermined default value for each OBO-related parameter. Inthis case, when the unassociated wireless communication terminalreceives information on the OBO-related parameters from the basewireless communication terminal, the unassociated wireless communicationterminal may set the OBO-related parameters according to the informationon the OBO-related parameters.

In a specific embodiment, when an unassociated wireless communicationterminal uses a predetermined default value for each OBO-relatedparameter, even if the unassociated wireless communication terminalreceives information on the OBO-related parameters from the basewireless communication terminal, the OBO-related parameters may not beset according to the information on the OBO-related parameters. In aspecific embodiment, when an unassociated wireless communicationterminal uses a predetermined default value for each OBO-relatedparameter, performs random access to the first base wirelesscommunication terminal, and performs random access to the second basewireless communication terminal, the unassociated wireless communicationterminal may not initiate the OBO procedure. For example, when anunassociated wireless communication terminal uses a predetermineddefault value for each OBO-related parameter, performs random access tothe first base wireless communication terminal, and performs randomaccess to the second base wireless communication terminal, theunassociated wireless communication terminal may use the OBO countervalue used in the OBO procedure for the first base wirelesscommunication terminal in the random access of the second base wirelesscommunication terminal.

In the embodiment of FIG. 24, when the UORA parameter set element is notreceived from the base wireless communication terminal, the firststation STA1 sets OCWmin to a default value of OCWmin and sets OCWmax toan OCWmax value. In this case, the first station STA1 initiates the OBOprocedure and selects 10 as a random integer within the OCW. The firststation STA1 sets the randomly selected 10 as the OBO count.

The first station STA1 receives the beacon frame from the first AP AP1and obtains the UORA parameter set element from the beacon frame. Thefirst station STA1 does not initialize the OBO procedure but maintainsthe value of the OBO-related parameter as it is.

The first station STA1 receives a trigger frame indicating two RUsallocated for random access from the first AP AP1. In this case, thefirst station STA1 decrements the OBO counter by 2 and sets the OBOcounter to 8.

In addition, the first station STA1 receives a trigger frame indicatingtwo RUs allocated for random access from the second AP AP2. In thiscase, the first station STA1 decrements the OBO counter by 2 and setsthe OBO counter to 6.

FIG. 25 shows the random access operation of an associated wirelesscommunication terminal according to an embodiment of the presentinvention.

The unassociated wireless communication terminal may transmit themanagement frame by randomly accessing the base wireless communicationterminal. Specifically, the unassociated wireless communication terminalmay transmit at least one of a probe request frame, an authenticationrequest frame, and an association request frame by randomly accessingthe base wireless communication terminal. When a wireless communicationterminal transmits a trigger-based PPDU in response to a trigger frame,the wireless communication terminal may perform transmission in theformat of Aggregate-MAC Protocol Data Unit (A-MPDU) according to a MACpadding rule. However, since the probe request frame, the authenticationrequest frame, and the association request frame are MAC ManagementProtocol Data Units (MMPDUs) that do not request an immediate response,transmission using A-MPDU may not be allowed. In this case, an immediateresponse may indicate that a response is transmitted within apredetermined period within one transmission opportunity (TXOP). Thepredetermined period may be an SIFS. It may be allowed to aggregateMMPDUs to the A-MPDU to transmit the A-MPDU in order for transmissionthrough the random access of the unassociated wireless communicationterminal. In this case, the MMPDU may include at least one of a proberequest frame, an authentication request frame, an association requestframe, and a reassociation request frame. Specifically, among thecontexts of the contents of the A-MPDU, the transmission of the MMPDUmay be included in a context including data that does not request animmediate response. In a specific embodiment, a probe request frame, anauthentication request frame, and an association request frame may beregulated with the type of MPDU that can be combined in the context ofdata that does not require an immediate response among the contexts ofthe contents of A-MPDU. In yet another specific embodiment, the contextfor the content of the A-MPDU may be defined. Specifically, it may beregulated that the context for the association procedure is set, theA-MPDUs defined in the context for the association procedure do notrequire an immediate response, and a QoS Null frame or an Action No ACKframe can be aggregated with the MMPDU. For example, it may be regulatedthat the A-MPDUs defined in the context for the association procedure donot require an immediate response and a QoS Null frame or an Action NoACK frame is allowed to be aggregated with a probe request frame, anauthentication request frame, or an association request frame.

In the embodiment of FIG. 25, the unassociated first station STA1receives a beacon frame from the AP. The first station STA1 obtains theUORA parameter set element from the beacon frame and initializes the OBOprocedure according to the obtained UORA parameter set element. Thefirst station STA1 sets the OBO counter to 3. The first station STA1receives a trigger frame indicating four RUs allocated for random accessfrom the AP. The first station STA1 decrements the OBO counter to 0based on the trigger frame. Therefore, the first station STA1 transmitsa trigger-based PPDU (HE TRIG PPDU) including the A-MPDU to which theprobe request frame or the association request frame is aggregated tothe AP through the RU allocated for the random access. The AP transmitsa Multi-STA BlockAck (M-BA) for a plurality of stations.

When the wireless communication terminal performing the random access isscheduled to transmit the uplink transmission by the trigger frame, theoperation of the wireless communication terminal will be described withreference to FIG. 26.

FIG. 26 shows a random access operation of a wireless communicationterminal when a wireless communication terminal according to anembodiment of the present invention schedules uplink transmission by atrigger frame.

When a wireless communication terminal performing random access isscheduled for uplink transmission by a trigger frame, whether thecorresponding wireless communication terminal can decrement the OBOcounter based on the RU allocated for the random access indicated by thetrigger frame may be a problem. Even when a wireless communicationterminal performing random access is scheduled for uplink transmissionby a trigger frame, if the OBO counter is decremented based on the RUallocated for the random access indicated by the trigger frame, thecorresponding wireless communication terminal may have an excessivelyhigher priority than the other wireless communication terminals.Therefore, the equality between wireless communication terminals can beviolated. When a wireless communication terminal performing randomaccess is scheduled for uplink transmission by a trigger frame, thecorresponding wireless communication terminal can maintain the OBOcounter regardless of the number of RUs allocated for the random accessindicated by the trigger frame.

The trigger frame may indicate that carrier sensing is required when awireless communication terminal scheduled for uplink transmission by thetrigger frame performs uplink transmission. In this case, when it isdetermined that the RU to be used for uplink transmission is busy basedon a result of the carrier sensing, the corresponding wirelesscommunication terminal may not attempt uplink transmission.Specifically, the trigger frame may indicate that carrier sensing isrequired when a wireless communication terminal scheduled for uplinktransmission by the trigger frame performs uplink transmission using theCS required field. Also, the carrier sensing may include an EnergyDetect (ED). When it is determined by the carrier sensing that the RU tobe used for uplink transmission is busy, the random access operation ofthe wireless communication terminal scheduled for the uplinktransmission by the trigger frame is a problem. This is because uplinktransmission is indicated by the trigger frame but the correspondingwireless communication terminal does not perform the uplinktransmission.

When the trigger frame schedules uplink the transmission of a wirelesscommunication terminal performing random access and indicates thatuplink transmission requires carrier sensing, a wireless communicationterminal performing random access may operate as follows. Whenit isdetermined by the carrier sensing that the RU to be used for uplinktransmission is busy, the wireless communication terminal performing therandom access may decrement the OBO counter based on the RU allocatedfor the random access indicated by the trigger frame. Specifically, thewireless communication terminal performing the random access maydecrement the OBO counter by the number of RUs allocated for the randomaccess indicated by the trigger frame. Also, when it is determined bythe carrier sensing that the RU to be used for uplink transmission isbusy, even if the OBO counter is 0 or the OBO counter reaches 0, thewireless communication terminal performing the random access maymaintain the OBO counter as 0 and may not attempt uplink transmission.In another specific embodiment, when it is determined by the carriersensing that the RU to be used for uplink transmission is busy and theOBO counter is 0 or the OBO counter reaches 0, the wirelesscommunication terminal performing the random access may randomly selectany one of the RUs allocated for the random access and attempt uplinktransmission.

In the embodiment of FIG. 26, the first station STA1 receives a beaconframe from the AP. The first station STA1 obtains the UORA parameter setelement from the beacon frame and initializes the OBO procedureaccording to the obtained UORA parameter set element. The first stationSTA1 sets the OBO counter to 3. The first station STA1 receives atrigger frame indicating the four RUs allocated for the random accessand scheduling the uplink transmission of the first station STA1 fromthe AP. Since the trigger frame schedules the uplink transmission of thefirst station STA1, the first station STA1 maintains the OBO counter asit is. Also, the first station STA1 transmits the TB PPDU (HE TRIG PPDU)according to the information indicated by the trigger frame to the AP.The AP transmits a Multi-STA BlockAck (M-BA) for a plurality ofstations.

In the above-described embodiments, it is described that the wirelesscommunication terminal can obtain information on the OBO counter fromthe beacon frame. In such a way, the wireless communication terminal canobtain information on the BSS from the beacon frame. Also, the basewireless communication terminal may periodically transmit a beacon frameto signal information on the BSS. A specific transmission method for thebeacon frame will be described with reference to FIG. 27 to FIG. 35.

FIG. 27 shows a legacy PPDU format according to an embodiment of thepresent invention.

The types of legacy PPDUs that can be transmitted by the legacy wirelesscommunication terminal may include at least one of Non-HT PPDU, HT-mixedPPDU, HT-greenfield PPDU, and VHT PPDU.

FIG. 27(a) shows the format of a non-HT PPDU. The Non-HT PPDU formatincludes a Short Training field including a relatively short trainingsignal, a Long Training field including a relatively long trainingsignal, a Signal field including signaling information, and a Data fieldincluding a payload of the PPDU. FIG. 27(b) shows the format of theHT-mixed PPDU. The HT-mixed PPDU includes L-STF, L-LTF and L-SIG fieldsfor legacy wireless communication terminals that do not support HT-mixedPPDUs. In addition, the HT-mixed PPDU includes an HT-SIG field includingsignaling information, an HT-STF including a relatively short trainingsignal, at least one HT-LTF including a relatively long training signal,and a Data field including a payload of the PPDU. FIG. 27(c) shows theformat of the HT-greenfield PPDU. The HT-greenfield PPDU includes anHT-GF-STF including a relatively short training signal and an HT-SIGfield including signaling information, at least one HT-LTF including arelatively long training signal, and a Data field including a payload ofthe PPDU. FIG. 27(d) shows the format of the VHT PPDU. The VHT PPDUincludes L-STF, L-LTF and L-SIG fields for legacy wireless communicationterminals that do not support VHT PPDU. In addition, the VH PPDUincludes a VHT-SIG-A field including signaling information, a VHT-STFincluding a relatively short training signal, at least one VHT-LTFincluding a relatively long training signal, and a Data field includinga payload of the PPDU. In addition, the VHT PPDU may include a VHT-SIG-Bfield for signaling additional information.

FIG. 28 shows a non-legacy PPDU format according to an embodiment of thepresent invention.

A wireless communication terminal according to an embodiment of thepresent invention may support one or more non-legacy PPDU formats. Also,the wireless communication terminal according to the embodiment of thepresent invention may select and use any one of a plurality ofnon-legacy PPDU formats according to the use and purpose of transmittingthe PPDU. Specifically, the wireless communication terminal can supportat least one of HE SU PPDU, HE MU PPDU, HE extended range SU PPDU, andHE trigger-based PPDU. The HE-SIG-A field and the HE-SIG-B field of thenon-legacy PPDU may be referred to as a Pre-HE modulated field. Inaddition, the HE-STF, HE-LTF, and Date fields of the non-legacy PPDU maybe referred to as HE modulated fields. The Pre-HE modulated fields andHE modulated fields can be modulated with different numerology.

FIG. 28(a) shows the format of the HE SU PPDU. The wirelesscommunication terminal may use the HE SU PPDU for single user (SU)transmission. The HE SU PPDU may include L-STF, L-LTF and L-SIG fieldsfor legacy wireless communication terminals. Also, the HE SU PPDUincludes a RL-SIG for signaling a non-legacy PPDU, a HE-SIG-A fieldincluding signaling information, a HE-STF including a relatively shorttraining signal, at least one HE-LTF including a relatively longtraining signal, and a Data field including a payload of the PPDU. Inaddition, the HE SU PPDU may include a Packet Extension (PE) field forsecuring processing time. The duration of the PE field may be determinedby the TXVECTOR parameter PE_DURATION. HE SU PPDU can deliver one PSDU.

FIG. 28(b) shows the format of the HE MU PPDU. The wirelesscommunication terminal may use the HE MU PPDU for transmission to one ormore users. In this case, the wireless communication terminal may notuse the HE MU PPDU in response to the trigger. The HE MU PPDU has aformat similar to that of the HE SU PPDU and may further include anHE-SIG-B field as compared to the HE SU PPDU. The HE-SIG-B fieldincludes information for Multi User (MU) transmission. The HE MU PPDUmay deliver more than one PSDU.

FIG. 28(c) shows the format of the HE trigger-based PPDU. In theembodiments described above, a TB PPDU may refer to an HE trigger-basedPPDU. The wireless communication terminal may use the HE trigger-basedPPDU for the response to the trigger frame or the UL MU ResponseScheduling A-Control field. HE trigger-based PPDUs may include HE-STFsincluding longer durations than that of the HE SU PPDU format.

FIG. 28(d) shows the format of the HE extended range SU PPDU. Thewireless communication terminal may use the HE extended range SU PPDUfor extended range transmission. The HE extended range SU PPDU has aformat similar to the HE SU PPDU, and the duration of the HE-SIG-A fieldof the HE extended range SU PPDU is twice the duration of the HE-SIG-Afield of the HE SU PPDU. The wireless communication terminal can performtransmission using four symbols. For example, four symbols can betransmitted in the HE-SIG-A field of the HE extended range SU PPDU. Thefour symbols used to transmit the HE-SIG-A field may be symbols that arerepeated in the time domain. The four symbols transmitting the HE-SIG-Afield are referred to as HE-SIG-A1, HE-SIG-A2, HE-SIG-A3 and HE-SIG-A4in time order. In this case, HE-SIG-Al and HE-SIG-A2 may transmit thesame signal, and HE-SIG-A3 and HE-SIG-A4 may transmit the same signal.Also, when transmitting the HE extended range SU PPDU, the wirelesscommunication terminal may boost the transmission power by 3 dB comparedto the case of transmitting L-STF and L-LTF of other non-legacy PPDUs.Also, when transmitting four extra tones (subcarrier index k=−28, −27,27, and 28) of the L-SIG field and the RL-SIG field, the wirelesscommunication terminal may boost the transmission power by 3 dB comparedto when transmitting L-STF and L-LTF of other non-legacy PPDUs. Throughthese operations, the wireless communication terminal can increase thereception probability of the HE extended range SU PPDU.

FIG. 29 shows the coverage of the HE extended range SU PPDU and thetransmission coverage of the legacy PPDU according to the embodiment ofthe present invention.

As described with reference to FIG. 28, when transmitting the HEextended range SU PPDU, the wireless communication terminal performsvarious operations for long distance transmission. Therefore, thetransmission coverage of the HE extended range SU PPDU is wider than thetransmission coverage of the legacy PPDU. Due to this, even a wirelesscommunication terminal that can receive the HE extended range SU PPDUmay not receive the legacy PPDU format. For example, in the situationshown in FIG. 29, the transmission coverage of the HE extended range SUPPDU is wider than that of the legacy PPDU (non-HE PPDU). Therefore, thefirst station STA1 may receive both the legacy PPDU (non-HE PPDU) andthe HE extended range SU PPDU. The second station STA2 may receive onlythe HE extended range SU PPDU without receiving the legacy PPDU (non-HEPPDU). When there is information to be transmitted through the legacyPPDU format, the wireless communication terminal located outside thecoverage of the legacy PPDU format can not use the information. Thewireless communication terminal may use the legacy PPDU format totransmit the beacon frame. Although the wireless communication terminalslocated outside the coverage of the legacy PPDU format can communicatewith the base wireless communication terminal using the HE extendedrange SU PPDU, it can not receive the BSS information and thus, can notcommunicate with the base wireless communication terminal. Therefore,the base wireless communication terminal may transmit the dual beaconframe. This will be described with reference to FIG. 30.

FIG. 30 shows a dual beacon transmission operation of the base wirelesscommunication terminal according to an embodiment of the presentinvention.

The base wireless communication terminal may transmit a beacon frameusing a plurality of PPDU formats. Specifically, the base wirelesscommunication terminal may transmit a beacon frame using two PPDUformats having different transmission coverage. The wirelesscommunication terminal may transmit the beacon frame using the legacyPPDU format and transmit the beacon frame using the PPDU format for widerange transmission. In this case, the PPDU format for wide rangetransmission may be the HE extended range SU PPDU described above.Through this operation, the base wireless communication terminal mayincrease the possibility that the wireless communication terminal aroundthe base wireless communication terminal receives the beacon frame. Forconvenience of explanation, the fact that a base wireless communicationterminal transmits a beacon frame using two PPDU formats havingdifferent transmission coverage is referred to as a dual beacon.

The base wireless communication terminal may transmit a beacon framebased on a predetermined period. In this case, a time point at which thebase wireless communication terminal attempts to transmit the beaconframe may be referred to as a target beacon transmission time (TBTT).The TBTT may be continued at predetermined time intervals. In this case,the predetermined time interval may be referred to as a beacon interval.When the channel on which the base wireless communication terminaltransmits a beacon frame is busy, the base wireless communicationterminal may attempt to transmit a beacon frame again after a scheduledtime. For example, when the channel on which the base wirelesscommunication terminal transmits a beacon frame is idle, the basewireless communication terminal may transmit a beacon frame.

The base wireless communication terminal may attempt to transmit thelegacy PPDU including the beacon frame in the TBTT and attempt totransmit the PPDU for wide range transmission including the beacon frameafter a predetermined time from the TBTT. At this point, thepredetermined time may be half of the time interval between TBTTs. Forexample, the TBTT of the beacon frame included in the legacy PPDU may bea timing synchronization function (TSF) value 0, and the TBTT of thebeacon frame included in the legacy PPDU may be repeated for each beaconinterval. The TBTT of the beacon frame included in the PPDU for widerange transmission may be a time point at which the half of the beaconinterval from the TSF value 0 elapses. In addition, the TBTT of thebeacon frame included in the PPDU for wide range transmission may bealso repeated for each beacon interval.

The base wireless communication terminal may signal whether to use thedual beacon using the Operation element. In this case, the Operationelement may be an HE Operation element. In addition, each of the beaconframes transmitted through different PPDU formats may include differenttypes of signaling information. Specifically, each of the beacon framestransmitted through different PPDU formats may include different typesof elements.

In the embodiment of FIG. 30, the base wireless communication terminalattempts to transmit a legacy PPDU including a beacon frame in a TBTTfor a legacy PPDU including a beacon frame. The base wirelesscommunication terminal transmits a legacy PPDU including a beacon frame,and the first station STA1 receives a legacy PPDU including a beaconframe. The second station STA2, which is farther from the base wirelesscommunication terminal than the first station STA1, does not receive thelegacy PPDU including the beacon frame.

At the time point that elapses by the half of the beacon interval of thelegacy PPDU including the beacon frame from the TBTT for the legacy PPDUincluding the beacon frame, the base wireless communication terminalattempts to transmit the HE extended range SU PPDU including the beaconframe. The base wireless communication terminal transmits the HEextended range SU PPDU including the beacon frame and the first stationSTA1 and the second station STA2 receive the HE extended range SU PPDUincluding the beacon frame.

At the time point that elapses by the beacon interval from the TBTT forthe legacy PPDU including the beacon frame, the base wirelesscommunication terminal attempts to transmit a legacy PPDU including abeacon frame. At the time point that elapses by half of the beaconinterval from this time, the base wireless communication terminalattempts to transmit the HE extended range SU PPDU including the beaconframe.

The base wireless communication terminal may signal information on aspecific time point using the TBTT described above. For example, thebase wireless communication terminal may signal the change start timepoint of the BSS color, which is an identifier indicating the BSS, usingthe TBTT. This will be described in more detail with reference to FIG.31.

FIG. 31 shows a format of a BSS Color Change Announcement elementaccording to an embodiment of the present invention.

The base wireless communication terminal may transmit a beacon frameincluding a BSS Color Change Announcement element to notify a change inBSS color and a new BSS color value. In this case, the BSS Color ChangeAnnouncement element may include a field indicating a time point atwhich the BSS color is changed. In addition, the BSS Color ChangeAnnouncement element may include a field indicating the value of thechanged BSS Color. For example, the BSS Color Change Announcementelement may include a Color Switch Countdown field. The Color SwitchCountdown field may indicate the number of TBTTs remaining until the BSScolor change time point. The BSS Color Change Announcement element mayinclude a New BSS Color Information field. The New BSS Color Informationfield may indicate a new BSS color value to be used as the BSS color ofthe corresponding BSS. The New BSS Color Information field may includethe New BSS Color subfield, and the New BSS Color subfield may representthe value of the new BSS color to be used as the BSS color of thecorresponding BSS. The specific format of the BSS Color ChangeAnnouncement element may be the same as that shown in FIG. 31.

For convenience of explanation, the TBTT in which the Color SwitchCountdown value reaches 0 and the BSS color is changed is referred to asa BSS Color change TBTT. Before reaching the BSS Color change TBTT, thebase wireless communication terminal inserts the BSS color value beforethe BSS change into the BSS Color subfield of the HE Operation element.In addition, when reaching the BSS Color change TBTT, the base wirelesscommunication terminal sets the BSS Color Disabled subfield of the HEOperation element to 0, inserts the changed value of BSS color into theBSS Color subfield of the HE Operation element, and starts using thechanged value of the BSS color. In addition, the wireless communicationterminal receiving the BSS Color Change Announcement element may use thechanged value of BSS color from the BSS Color change TBTT. In this case,the wireless communication terminal obtained the changed value of theBSS color from the BSS Color Change Announcement element.

In order for all wireless communication terminals in the BSS to use thesame BSS color value, the base wireless communication terminal and thewireless communication terminal can operate as follows. The basewireless communication terminal transmitting the BSS Color ChangeAnnouncement element may use the previous BSS color value until the BSSColor change TBTT is reached, and use the changed value of the BSS Colorafter the BSS Color change TBTT. Also, until the base wirelesscommunication terminal transmitting the BSS Color Change Announcementelement reaches the BSS Color change TBTT, it may not be allowed tochange the BSS Color change TBTT indicated by the BSS Color ChangeAnnouncement element. When the base wireless communication terminal usesthe dual beacon, the BSS color change time point can be determineddifferently according to the format of the PPDU that the wirelesscommunication terminal can receive. This will be described withreference to FIG. 32.

FIG. 32 shows a BSS color changing operation of a base wirelesscommunication terminal when the base wireless communication terminaluses dual beacons according to an embodiment of the present invention.

Due to the distance between the wireless communication terminal and thebase wireless communication terminal, the wireless communicationterminal may receive only one kind of PPDU format among the PPDU formatsused for dual beacons. In this case, the wireless communication terminalreceiving only one PPDU format of the PPDU format used for the dualbeacon may determine the BSS Color change TBTT differently from thewireless communication terminal receiving all the PPDU formats used forthe dual beacon. Specifically, since the wireless communication terminalmay not recognize the transmission of the beacon frame included in thePPDU format that the wireless communication terminal may not receive,the number of TBTTs remaining until the BSS color change may not beaccurately determined. In addition, a wireless communication terminalreceiving all of the PPDU formats used for dual beacons can confuse howto set the TBTT criteria in determining the BSS Color change TBTT. Forexample, a wireless communication terminal receiving all of the PPDUformats used for a dual beacon may have a difficulty in determiningwhether the value indicated by the Countdown field indicates a TBTT ofall kinds of PPDU format including a beacon frame or only a TBTT of aspecific kind of PPDU format including a beacon frame.

In the embodiment of FIG. 32, the base wireless communication terminalattempts to transmit a legacy PPDU including a beacon frame in a TBTTfor a legacy PPDU including a beacon frame. The base wirelesscommunication terminal transmits a legacy PPDU including a beacon frame,and the first station STA1 receives a legacy PPDU including a beaconframe. The second station STA2, which is farther from the base wirelesscommunication terminal than the first station STA1, does not receive thelegacy PPDU including the beacon frame.

At the time point that elapses by the half of the beacon interval of thelegacy PPDU including the beacon frame from the TBTT for the legacy PPDUincluding the beacon frame, the base wireless communication terminalattempts to transmit the HE extended range SU PPDU including the beaconframe. The base wireless communication terminal transmits the HEextended range SU PPDU including the beacon frame and the first stationSTA1 and the second station STA2 receive the HE extended range SU PPDUincluding the beacon frame.

In this case, the beacon frame included in the legacy PPDU signals theBSS Color change TBTT based on the TBTT of the beacon frame included inthe legacy PPDU. The beacon frame included in the legacy PPDU may signalthe remaining TBTT count until the first time point (BSS Color changeTBTT 1) at which the BSS color is changed and the legacy PPDU includingthe first beacon frame is transmitted. The beacon frame included in thePPDU for wide range transmission signals the BSS Color change TBTT basedon the TBTT of the beacon frame included in the PPDU for wide rangetransmission. The beacon frame included in the PPDU for wide rangetransmission can signal the remaining TBTT count until the second timepoint (BSS Color change TBTT 2) at which the BSS color is changed andthe PPDU for wide range transmission including the first beacon frame istransmitted. Since the first station STA1 can receive two types of PPDUformats including beacon frames, it may not determine at which timepoint among the first time point (BSS Color change TBTT 1) or the secondtime point (BSS Color change TBTT 2) the BSS color changes. Also, thesecond station STA2 does not receive information on the first time point(BSS Color change TBTT1). Therefore, the BSS color change time points ofthe first station STA1 and the second station STA2 may be different. Asa result, interference may occur because of wireless communicationterminals included in the same BSS and using different BSS color values.

The wireless communication terminal may perform operations other thanthe BSS color change operation based on the TBTT. For example, thewireless communication terminal may receive a UORA parameter element setin relation to random access in the TBTT and perform an operationaccording to the reception of the UORA parameter element set. Theoperation according to the reception of the UORA parameter element setmay include at least one of OBO related parameter setting and OBOprocedure initialization. As a result, when the base wirelesscommunication terminal uses the dual beacon, there may be a problem thatthe time point at which the wireless communication terminal receives theUORA parameter element set in relation to the random access and performsthe operation according to the reception of the UORA parameter elementset becomes unclear. In addition, a wireless communication terminallocated relatively close to the base wireless communication terminal mayreceive a UORA parameter element set more frequently than a wirelesscommunication terminal located relatively far from the base wirelesscommunication terminal. Accordingly, a wireless communication terminallocated relatively close to the base wireless communication terminal mayperform an OBO procedure more frequently than a wireless communicationterminal located relatively far from the base wireless communicationterminal. As a result, equality between wireless communication terminalsfor random access may be a problem. For convenience of explanation, anoperation in which a wireless communication terminal determines anoperation execution time point based on a TBTT is referred to as aTBTT-based operation. An embodiment in which the wireless communicationterminal can perform the TBTT-based operation without any problem evenwhen the base wireless communication terminal uses the dual beacon willbe described with reference to FIG. 33 to FIG. 34.

FIG. 33 shows a BSS color changing operation of a base wirelesscommunication terminal when the base wireless communication terminaluses dual beacons according to another embodiment of the presentinvention.

When the base wireless communication terminal uses dual beacons, thewireless communication terminal may perform a TBTT-based operation in aTBTT of a beacon frame included in one PPDU format and may not perform aTBTT-based operation in a TBTT of a beacon frame included in anotherPPDU format. Specifically, the wireless communication terminal mayperform a TBTT-based operation on the TBTT of the beacon frame includedin the legacy PPDU and may not perform the TBTT-based operation on theTBTT of the beacon frame included in the PPDU for wide rangetransmission. In another specific embodiment, specifically, the wirelesscommunication terminal may perform the TBTT-based operation on the TBTTof the beacon frame included in the PPDU for wide range transmissionwithout performing the TBTT-based operation on the TBTT of the beaconframe included in the legacy PPDU. For convenience of explanation, theformat of the PPDU including the beacon frame transmitted at the TBTT atwhich the wireless communication terminal performs the TBTT-basedoperation is referred to as a reference PPDU format. Beacons included inthe PPDU format other than the reference PPDU format may also signalinformation related to the TBTT reference operation. In this case, theinformation related to the TBTT reference operation signaled by thebeacon included in the reference PPDU format and the information relatedto the TBTT reference operation signaled by the beacon included in thePPDU format other than the reference PPDU format may indicate the sameinformation.

In such an embodiment, the BSS Color Change Announcement element mayindicate the same BSS color change time point regardless of the formatof the PPDU including the BSS Color Change Announcement element. Also,the Color Switch Countdown field may indicate the number of times thereference PPDU format including the remaining beacon frame istransmitted before the BSS color is changed. If the Color SwitchCountdown field included in the PPDU format other than the referencePPDU format is 0, the Color Switch Countdown field may indicate that theBSS color is changed when the reference PPDU format including the beaconframe is transmitted. For example, when the wireless communicationterminal changes the BSS color in the TBTT of the beacon frame includedin the legacy PPDU, the Color Switch Countdown field may indicate thenumber of times of transmitting a legacy PPDU including a remainingbeacon frame before the BSS color is changed. In this case, when theColor Switch Countdown field of the beacon frame included in the PPDUfor wide range transmission indicates 0, the wireless communicationterminal may determine that the BSS color is changed at the TBTT of thebeacon frame included in the legacy PPDU transmitted after thecorresponding beacon frame. Also, when the Color Switch Countdown fieldof the beacon frame included in the legacy PPDU indicates 0, thewireless communication terminal may determine that the BSS color ischanged at the TBTT of the corresponding beacon frame.

In another specific embodiment, when the wireless communication terminalchanges the BSS color in the TBTT of the beacon frame included in thePPDU for wide range transmission, the Color Switch Countdown field mayindicate the number of times the PPDU for wide range transmissionincluding the remaining beacon frame is transmitted before the BSS coloris changed. In this case, when the Color Switch Countdown field of thebeacon frame included in the legacy PPDU indicates 0, the wirelesscommunication terminal can determine that the BSS color is changed inthe TBTT of the beacon frame included in the PPDU for wide rangetransmission transmitted after the corresponding beacon frame. Also,when the Color Switch Countdown field of the beacon frame included inthe PPDU for wide range transmission indicates 0, the wirelesscommunication terminal can determine that the BSS color is changed inthe TBTT of the corresponding beacon frame.

In the embodiment of FIG. 33, the BSS color is changed at the TBTT ofthe beacon frame included in the legacy PPDU (non-HE format). Therefore,both the beacon frame included in the HE extended range SU PPDU and thebeacon frame included in the legacy PPDU (non-HE format) signal the TBTTof the beacon frame included in the legacy PPDU (non-HE format) as theBSS color change time point. Therefore, the first station STA1 and thesecond station STA2 can change the BSS color based on the same timepoint. Among the operations of the base wireless communication terminal,the first station STA1, and the second station STA2, the description ofthe same operation as that in the embodiment of FIG. 31 is omitted.

In another specific embodiment, the wireless communication terminal mayupdate the OBO-related parameter based on the UORA parameter set elementin the TBTT of the beacon frame included in the PPDU for wide rangetransmission, and may not update the OBO-related parameter based on theUORA parameter set element in the TBTT of the beacon frame included inthe legacy PPDU. Also, the wireless communication terminal mayinitialize the OBO procedure based on the UORA parameter set element inthe TBTT of the beacon frame included in the PPDU for wide rangetransmission, and may not initialize the OBO procedure based on the UORAparameter set element in the TBTT of the beacon frame included in thelegacy PPDU.

FIG. 34 shows a BSS color changing operation of a base wirelesscommunication terminal when the base wireless communication terminaluses dual beacons according to another embodiment of the presentinvention.

When the base wireless communication terminal uses dual beacons, thebase communication terminal may signal information related to theTBTT-based operation through a beacon frame included in one PPDU format,and may not signal information related to TBTT-based operation throughbeacon frames included in other types of PPDU formats. Specifically, thebase wireless communication terminal may signal information related tothe TBTT-based operation through the beacon frame included in the legacyPPDU, and may not signal information related to the TBTT based operationthrough the beacon frame included in the PPDU for wide rangetransmission. Also in these embodiments, the reference PPDU formatdescribed with reference to FIG. 33 may be designated. The referencePPDU format may be a PPDU format that includes a beacon signalinginformation related to the TBTT based operation. In addition, the PPDUformat including a beacon signaling information related to theTBTT-based operation may be a format of a PPDU having a widertransmission coverage than other PPDU formats. This is because as thetransmission coverage of the PPDU format, which includes beaconssignaling information related to TBTT-based operations, is wider, morewireless communication terminals can receive information related to TBTTbased operation.

In a specific embodiment, the base wireless communication terminal maysignal the BSS Color Change Announcement element through the beaconframe included in the PPDU for wide range transmission and may notsignal the BSS Color Change Announcement element through the beaconframe included in the legacy PPDU. Even in this embodiment, thereference PPDU format may be designated. Specifically, the referencePPDU format may be a PPDU for wide range transmission.

In the embodiment of FIG. 34, the base wireless communication terminaltransmits the BSS Color Change Announcement element through the beaconframe included in the HE extended range SU PPDU and does not transmitthe BSS Color Change Announcement element through the beacon frameincluded in the legacy PPDU (non-HE format). Also, the BSS color ischanged based on the TBTT of the beacon frame included in the HEextended range SU PPDU. Among the operations of the base wirelesscommunication terminal, the first station STA1, and the second stationSTA2, the description of the same operation as that in the embodiment ofFIG. 31 is omitted.

In another specific embodiment, the base wireless communication terminalmay transmit the UORA parameter set element through the beacon frameincluded in the PPDU for wide range transmission and may not transmitthe UORA parameter set element through the beacon frame included in thelegacy PPDU.

The base wireless communication terminal may transmit the beacon frameusing the STBC. In this case, the transmitted beacon frame may bereferred to as an STBC beacon frame. When the base wirelesscommunication terminal uses both the STBC beacon frame and the beaconframe included in the HE extended range SU PPDU, the transmission timepoint of the STBC beacon frame and the transmission time point of the HEextended range SU PPDU may overlap. Also, it may be difficult for thewireless communication terminal receiving the beacon frame to determinewhich beacon frame is transmitted at which time point. Therefore, thebase wireless communication terminal may not operate the STBC beaconframe and the beacon frame included in the HE extended range SU PPDUtogether. For example, when the base wireless communication terminaluses the beacon frame included in the HE extended range SU PPDU, thebase wireless communication terminal may not use the STBC beacon frame.Further, when the base wireless communication terminal starts using thebeacon frame included in the HE extended range SU PPDU, the basewireless communication terminal may stop using the STBC beacon frame.

The base wireless communication terminal may indicate whether to use theSTBC beacon frame using the Dual Beacon field of the HT Operationelement. Also, the base wireless communication terminal may indicatewhether to use the beacon frame included in the HE extended range SUPPDU using the Dual Beacon field of the HT Operation element. When theDual Beacon field of the HT Operation element signals that any one ofthe STBC beacon frame and the beacon frame included in the HE extendedrange SU PPDU is used, the Dual Beacon field of the HT Operation elementmay indicate that other beacon frames are not used. For example, whenthe Dual Beacon field of the HE Operation element indicates that theSTBC beacon frame is used, the Dual Beacon field of the HE Operationelement may indicate that the beacon frame included in the HE extendedrange SU PPDU is not used. Therefore, when the Dual Beacon field of theHE Operation element is 1, the Dual Beacon field of the HE Operationelement may indicate that the STBC beacon frame is not used.

The wireless communication terminal may transmit one MPDU orAggregate-MPDU (A-MPDU) as a physical layer service data unit (PSDU) ofthe PPDU. In this case, the wireless communication terminal canaggregate a plurality of MPDUs to generate one Aggregate-MAC ProtocolData Unit (A-MPDU). The wireless communication terminal can increase thetransmission efficiency by transmitting the A-MPDU instead of dividingthe plurality of MPDUs into a plurality of PPDUs and transmitting theplurality of PPDUs. A specific format of the A-MPDU will be describedwith reference to FIG. 35.

FIG. 35 shows a format of an A-MPDU according to an embodiment of thepresent invention.

The A-MPDU may include the sequence of one or more A-MPDU subframes andan EOF Padding. The boundary between A-MPDU subframes may bedistinguished by the MPDU delimiter field. The MPDU may follow the MPDUdelimiter field. When the A-MPDU subframe is not the last A-MPDUsubframe, the A-MPDU subframe may include Padding Octets. The wirelesscommunication terminal may set padding octets so that the length of eachA-MPDU subframe is a multiple of 4 octets. The length of the Paddingsubfield included in the last A-MPDU subframe may be 0 to 3 octets.

The length of the MPDU delimiter field may be 4 octets. The specificformat of the MPDU delimiter field may be the same as that shown in FIG.35. In this case, the MPDU delimiter field may be a format of an MPDUdelimiter field transmitted by the non-DMG wireless communicationterminal. The MPDU delimiter field may include at least one of an EOFsubfield, a Reserved subfield, an MPDU Length subfield, a CRC subfield,and a Delimiter Signature subfield. The EOF subfield may be a 1-bitfield. The wireless communication terminal sets the MPDU Length subfieldof the A-MPDU subframe to 0 and sets the EOF subfield to 1, therebyindicating that the corresponding A-MPDU subframe is the EOF paddingsubframe. In addition, the wireless communication terminal sets the EOFsubfield to 1 and sets the MPDU Length subfield to a non-zero value toindicate that the corresponding A-MPDU subframe is a VHT single MPDU ora single MPDU (S-MPDU). The VHT single MPDU or single MPDU is the onlyone MPDU in the corresponding A-MPDU. The wireless communicationterminal may set the EOF field to 0 in other cases. The MPDU Lengthsubfield may indicate the length of the MPDU including the A-MPDUsubframe in octet units. When the A-MPDU subframe does not include anMPDU, the wireless communication terminal sets the MPDU Length field to0. The CRC subfield may include a CRC value for 16 bits included in theMPDU delimiter field. The CRC field may be an 8-bit field. The DelimiterSignature subfield may include a value set to identify the MPDUdelimiter. In this case, the set value may be 0x4E.

The length of the EOF Padding field may be variable. The EOF Paddingfield may include an EOF Padding subframe and EOF Padding Octets. TheEOF Padding field may optionally include one or more EOF Paddingsubframes. The MPDU delimiter field may include an MPDU Length field andan EOF field. The wireless communication terminal sets the MPDU Lengthsubfield of the A-MPDU subframe to 0 and sets the EOF subfield to 1,thereby indicating that the corresponding A-MPDU subframe is the EOFpadding subframe. The length of the EOF Padding Octets subfield may be 0to 3 octets.

As described above, the wireless communication terminal may signalinformation on the A-MPDU subframe through the value of the EOF field.In this case, the wireless communication terminal may configure theA-MPDU according to the following rules.

-   -   The A-MPDU subframe in which the EOF subfield is set to 0 in the        A-MPDU is not located after the A-MPDU subframe in which the EOF        subfield is set to 1.    -   The A-MPDU subframe in which the EOF subfield is set to 1 and        the MPDU Length subfield is set to 0 in the A-MPDU is not        located before the A-MPDU subframe including the VHT single        MPDU.

In addition, the wireless communication terminal may set a predeterminedvalue in the EOF subfield and solicit an immediate response to the MPDUincluded in the A-MPDU. Specifically, the wireless communicationterminal transmitting the PPDU solicit an immediate response by settingthe Ack Policy field of the QoS data frame or the QoS Null frame,transmitting a specific type of frame (for example, an Action frame, aBAR frame, or an MU-BAR frame), or setting a the EOF subfield topredetermined value when a frame is transmitted through an A-MPDU or amulti-TID A-MPDU.

The Multi-TID A-MPDU represents an MPDU generated by associating aplurality of MPDUs having different traffic identifiers (TIDs).Specifically, the multi-TID A-MPDU may be an A-MPDU including aplurality of QoS Data frames having different TIDs. The wirelesscommunication terminal may solicit a specific type of response to theMPDU included in the A-MPDU subframe using the values of the subfieldsof the MPDU delimiter field included in the Multi-TID A-MPDU.Specifically, when the wireless communication terminal generates theMulti-TID A-MPDU, the wireless communication terminal may set the MPDULength subfield of the MPDU delimiter field to a non-zero value and setthe value of the EOF subfield to 0 to solicit an immediate ACK frametransmission for the QoS data frame or action frame included in theA-MPDU subframe corresponding to the MPDU delimiter field. In addition,the wireless communication terminal may set a plurality of noncontiguousMPDU delimiter fields in which the EOF subfield is 1 and the MPDU Lengthfield has a non-zero value, to solicit an ACK for an MPDU included ineach of a plurality of MPDU delimiter fields. In addition, the wirelesscommunication terminal may set a plurality of noncontiguous MPDUdelimiter fields in which the EOF subfield is 0 and the MPDU Lengthfield has a non-zero value to solicit a BlockAck for an MPDU included ineach of a plurality of MPDU delimiter fields. The wireless communicationterminal may aggregate A-MPDUs by combining an A-MPDU subframe includingthe MPDU delimiter field in which the EOF subfield is 1 and the MPDULength subfield is not 0 and an A-MPDU subframe including the MPDUdelimiter field in which the EOF subfield is 0 and the MPDU Lengthsubfield is not 0. In addition, the wireless communication terminal maynoncontiguously aggregate A-MPDU subframes having the same TID togenerate a Multi-TID A-MPDU.

The wireless communication terminal receiving the Multi-TID A-MPDU maytransmit the Multi-STA BlockAck in response to the Multi-TID A-MPDU. Inthis case, the Multi-STA BlockAck may include the following Per STA Infofield.

-   -   The Per STA Info field indicating the ACK for successful        reception of the MPDU corresponding to the MPDU Length field in        which the EOF subfield value is 1 has a non-zero length (In this        case, the TID value of the MPDU may indicate the TID of the QoS        data frame or the QoS null frame. In addition, the TID value of        the MPDU may be 15, which represents the action frame.)    -   The Per STA Info field indicating the BlockAck for successful        reception of the MPDU corresponding to the MPDU Length field in        which the EOF subfilter value is 0 has a non-zero length (In        this case, the TID value of the MPDU may be the TID value of the        QoS data frame.)

A specific format of BlockAck will be described with reference to FIG.36.

FIG. 36 shows a concrete format of BlockAck according to an embodimentof the present invention.

The BlockAck frame may include at least one of a Frame Control field, aDuration field, an RA field, a TA field, a BA Control field, a BAInformation field, and an FCS field. The Frame Control field, theDuration field, the RA field, and the TA field correspond to a MACheader. When the BlockAck frame is not a Multi-STA BlockAck variant, thewireless communication terminal may set the RA field as the TA field ofthe frame that solicits the BlockAck frame. Also, when the BlockAckframe is not a Multi-STA BlockAck variant, the wireless communicationterminal may set the RA field as the address of the wirelesscommunication terminal transmitting the data/management frame that is anACK with the BlockAck frame.

When the BlockAck frame is that the Multi-STA BlockAck frame is aMulti-STA BlockAck variant and the value of the AID subfield of the PerSTA Info subfield included in the Multi-STA BlockAck variant is two ormore, the wireless communication terminal may set the RA field as abroadcast address. When the BlockAck frame is that the Multi-STABlockAck frame is a Multi-STA BlockAck variant and the value of the AIDsubfield of the Per STA Info subfield included in the Multi-STA BlockAckvariant is one, the wireless communication terminal may set the RA fieldas the address of the wireless communication terminal requesting theBlockAck or may set it as a broadcast address. When the BlockAck frameis that the Multi-STA BlockAck frame is a Multi-STA BlockAck variant andthe value of the AID subfield of the Per STA Info subfield included inthe Multi-STA BlockAck variant is one, the wireless communicationterminal may set the RA field as the address of the wirelesscommunication terminal requesting the BlockAck or may set it as theaddress of the wireless communication terminal transmitting thedata/management frame that is an ACK with the BlockAck frame. Inaddition, when the value of the AID subfield of the Per STA Infosubfield included in the Multi-STA BlockAck variant is one, a Multi-STABlockAck variant may include only one AID subfields of Per STA Infosubfield or a plurality of the AID subfield of Per STA Info subfieldsthat have the same value.

In addition, the BA Control field may include at least one of a BA AckPolicy subfield, a BA Type subfield, a TID_INFO subfield, and a Reservedsubfield, as shown in FIG. 36. The BA Type subfield may include at leastone of an existing Multi-TID subfield, Compressed Bitmap subfield, andGCR subfield. Specifically, B1 of the BA type may be the same as theexisting Multi-TID subfield. In addition, B2 of the BA Type may be thesame as the existing Compressed Bitmap subfield. In addition, B3 of theBA Type may be the same as the existing GCR subfield.

In a specific embodiment, the wireless communication terminal may signala kind of BlockAck frame using the BA Type subfield. The wirelesscommunication terminal may set the BA Type subfield to a predeterminedvalue to indicate that the BlockAck frame is a Multi-STA BlockAckvariant. For example, the wireless communication terminal may set theB1-B4 of the BA Type subfield to 1101 to indicate that the BlockAckframe is a Multi-STA BlockAck variant. The BlockAck frame, which is theMulti-STA BlockAck variant, may be referred to as a Multi-STA BlockAckframe. Also, the wireless communication terminal may indicate using theBA Type subfield whether a BlockAck frame is a Basic BlockAck, aCompressed BlockAck, a GLK-GCR BlockAck, a GCR BlockAck, an ExtendedCompressed BlockAck, a Multi-TID BlockAck, or a Multi-STA BlockAck.

Also, the information indicated by the TID_INFO subfield may varyaccording to the BlockAck frame variant type. Specifically, theinformation indicated by the TID_INFO subfield may vary according to thetype of the BlockAck frame. When the BlockAck frame is a Multi-STABlockAck, the TID_INFO subfield may be a reserved field.

In addition, the information indicated by the BA Information field mayvary according to the BlockAck frame variant type. Specifically, whenthe BlockAck frame is a Multi-STA BlockAck variant, the BA Informationfield may include one or more Per STA Info subfields of FIG. 37. Aspecific format of the Per STA Info subfield will be described in detailwith reference to FIG. 37. In this specification, receiving anMPDU/frame may refer to the successful reception of an MPDU or frame.Specifically, if the value of the frame check sequence (FCS) obtainedbased on the received MPDU/frame is equal to the value of the FCS field,the wireless communication terminal may determine that the MPDU/frame issuccessfully received.

FIG. 37 shows a Per STA Info subfield according to an embodiment of thepresent invention.

The BA Information field of the Multi-STA BlockAck may include one ormore Per STA Info fields.

The Per STA Info subfield may include a Per AID TID Info subfield. ThePer AID TID Info subfield may include at least one of an AID subfield,an Ack Type subfield, and a TID subfield. When a Multi-STA BlockAckframe is intended to be transmitted to a wireless communication terminalother than a base wireless communication terminal, the wirelesscommunication terminal may set the AID subfield to 11 LSBs of the AID ofthe corresponding wireless communication terminal. When a Multi-STABlockAck frame is intended to be transmitted to a wireless communicationterminal other than a base wireless communication terminal, the wirelesscommunication terminal may set the AID subfield to the AID of thecorresponding wireless communication terminal. When a Multi-STA BlockAckframe is intended to be transmitted to a base wireless communicationterminal, the wireless communication terminal may set the AID subfieldto 0.

One Multi-STA BlockAck frame may include a plurality of Per STA Infosubfields which the AID subfield having the same value. In this case,the values of the TID subfield of the plurality of Per STA Infosubfields may be different from each other.

The TID subfield indicates the TID of the frame that the Per AID TIDInfo subfield ACKs. When the Per AID TID Info subfield of the Multi-STABlockAck variant ACKs the management frame, the wireless communicationterminal may set the TID subfield to 15.

In addition, the Ack Type subfield may indicate whether a Block AckStarting Sequence Control subfield and a Block Ack Bitmap subfield ispresent or not in the Per STA Info subfield corresponding to the AckType subfield. This will be described in more detail with reference toFIG. 38.

FIG. 38 shows the context of a Per STA Info subfield according to anembodiment of the present invention.

When the Ack Type subfield is 1 and the value of the TID subfield of thePer AID TID Info subfield is less than or equal to 8 or 15, the Ack Typesubfield and the TID subfield may indicate that the Block Ack StartingSequence Control subfield and the Block Ack Bitmap subfield is notpresent. In this case, the Per STA Info subfield corresponding to theAck Type field may ACK that a single MPDU indicated by the TID subfieldof the Per AID TID Info subfield is received successfully.

In addition, when the Ack Type subfield is 1 and the value of the TIDsubfield of the Per AID TID Info subfield is 14, the Ack Type subfieldand the TID subfield may indicate that the Block Ack Starting SequenceControl subfield and the Block Ack Bitmap subfield is not present. Inthis case, the Per STA Info subfield corresponding to the Ack Type fieldmay ACK that all the MPDUs of the A-MPDU including a frame indicated bythe TID subfield of the Per AID TID Info subfield are receivedsuccessfully.

In addition, when the Ack Type subfield is 0, the Ack Type subfield mayindicate that a Block Ack Starting Sequence Control subfield and a BlockAck Bitmap subfield is present. In addition, the specific context of thePer STA Info subfield may be the same as that shown in FIG. 38.

A specific method of the wireless communication terminal receiving theMulti-TID A-MPDU to generate the Multi-STA BlockAck frame will bedescribed with reference to FIG. 39 to FIG. 40. For convenience ofexplanation, the wireless communication terminal transmitting theMulti-TID A-MPDU is referred to as a Multi-TID A-MPDU transmitter andthe wireless communication terminal receiving the Multi-TID A-MPDU isreferred to as a Multi-TID A-MPDU receiver.

FIGS. 39 to 40 show an A-MPDU configuration according to an embodimentof the present invention.

As described above, the wireless communication terminal may aggregateA-MPDUs by combining the A-MPDU subframe including the MPDU delimiterfield in which the EOF subfield is 1 and the MPDU Length subfield is not0 and the A-MPDU subframe including the MPDU delimiter field in whichthe EOF subfield is 0 and the MPDU Length subfield is not 0. Inaddition, the wireless communication terminal may noncontiguouslyaggregate A-MPDU subframes having the same TID to generate a Multi-TIDA-MPDU. When the EOF subfield of the MPDU delimiter field is 1 and theMPDU Length subfield is not 0, the Multi-TID A-MPDU receiver may ACK forthe MPDU corresponding to the MPDU delimiter field using the Per AID TIDInfo field in which the Block Ack Starting Sequence Control field andthe Block Ack Bitmap field are omitted. In addition, when the EOFsubfield of the MPDU delimiter field is 0 and the MPDU Length subfieldis not 0, the Multi-TID A-MPDU receiver may ACK for the MPDUcorresponding to the MPDU delimiter field using the Per AID TID Infofield including both the Block Ack Starting Sequence Control field andthe Block Ack Bitmap field. For an efficient Multi-STA BlockAck frameconfiguration, when a Multi-TID A-MPDU transmitter generates a Multi-TIDA-MPDU, the Multi-TID A-MPDU transmitter may limit the number of MPDUscorresponding to TIDs requesting ACKs other than BlockAck to one MPDUper TID. Specifically, when the Multi-TID A-MPDU transmitter aggregatesa Multi-TID A-MPDU, the Multi-TID A-MPDU transmitter may add the MPDUcorresponding to the MPDU delimiter field, in which the EOF subfield is1 and the MPDU Length subfield is not 0, to the Multi-TID A-MPDU, andthen may not add an MPDU having the same TID as the TID of thecorresponding MPDU to the Multi-TID A-MPDU.

Also, when an MPDU included in any one A-MPDU subframe corresponds to aspecific TID among the MPDUs included in the Multi-TID A-MPDU, theMulti-TID A-MPDU transmitter may set the EOF subfield of the A-MPDUsubframe to 1. When the MPDU included in any one A-MPDU subframe is theonly one MPDU corresponding to a specific TID in which the value of theMPDU Length field is not 0 among the MPDUs included in the Multi-TIDA-MPDU, the Multi-TID A-MPDU transmitter may set the EOF subfield of theA-MPDU subframe to 1. Also, when an MPDU included in any one A-MPDUsubframe does not correspond to a specific TID among the MPDUs includedin the Multi-TID A-MPDU, the Multi-TID A-MPDU transmitter may set theEOF subfield of the A-MPDU subframe to 0. When the MPDU included in anyone A-MPDU subframe is not the only one MPDU corresponding to a specificTID in which the value of the MPDU Length field is not 0 among the MPDUsincluded in the Multi-TID A-MPDU, the Multi-TID A-MPDU transmitter mayset the EOF subfield of the A-MPDU subframe to 0.

In a specific embodiment, when a Multi-TID A-MPDU transmitter uses aPPDU of a predetermined format for multi-TID A-MPDU transmission, theMulti-TID A-MPDU transmitter may set the EOF subfield according to theembodiments described above. For example, when the Multi-TID A-MPDUtransmitter uses a non-legacy PPDU for transmission of a Multi-TIDA-MPDU, the Multi-TID A-MPDU transmitter may set the EOF subfieldaccording to the embodiments described above. In this case, thenon-legacy PPDU may represent the PPDU format described with referenceto FIG. 28.

The Multi-TID A-MPDU receiver may generate Multi-STA BlockAck frame asfollows. When the Multi-TID A-MPDU receiver receives all the MPDUscorresponding to the MPDU delimiter field in which the EOF subfield is 0and the MPDU Length subfield is not 0, the Multi-TID A-MPDU receiver maydetermine that all the MPDUs in the Multi-TID A-MPDU that requestBlockAck are received. Also, when the EOF subfield of the MPDU delimiterfield corresponding to all the MPDUs not received by the multi-TIDA-MPDU receiver is 1 and the MPDU Length subfield is not 0, theMulti-TID A-MPDU receiver may determine that all the MPDUs requestingBlockAck, which is included in the Multi-TID A-MPDU, are received. Whenthe EOF subfield of the MPDU delimiter field corresponding to all theMPDUs not received by the multi-TID A-MPDU receiver is 1, the Multi-TIDA-MPDU receiver may determine that all the MPDUs requesting BlockAck,which is included in the Multi-TID A-MPDU, are received.

The multi-TID A-MPDU receiver may determine that the EOF subfield of theMPDU delimiter field corresponding to the not-received MPDU is 1according to the following embodiments. In the A-MPDU, when the A-MPDUsubframe in which the EOF subfield is set to 0 is limited to not beinglocated after the A-MPDU subframe in which the EOF subfield is set to 1,the multi-TID A-MPDU receiver may determine that the EOF subfield of theMPDU delimiter field corresponding to the not-received MPDU is 1according to the following embodiment. When the Multi-TID A-MPDUreceiver does not receive the MPDU included in the A-MPDU subframelocated behind the A-MPDU subframe including the MPDU delimiter field inwhich the EOF subfield is 1, the multi-TID A-MPDU receiver may determinethat the MPDU corresponding to the MPDU delimiter field in which the EOFsubfield is 1 is not received. In another specific embodiment, when theMulti-TID A-MPDU receiver receives the MPDU delimiter field and does notreceive the MPDU corresponding to the MPDU delimit field, the Multi-TIDA-MPDU receiver may check the value of the EOF subfield of the MPDUdelimiter field and determine whether the Multi-TID A-MPDU receiver doesnot receive the MPDU corresponding to the MPDU delimiter field in whichthe EOF subfield is 1.

Receiving all the MPDUs included in the Multi-TID A-MPDU and requestingBlockAck may represent receiving all the MPDUs having the TID of theMPDU corresponding to the MPDU delimiter field in which the EOF subfieldis 0 and the MPDU Length subfield is not 0 and which are included in theMulti-TID A-MPDU.

When the Multi-TID A-MPDU receiver receives all the MPDUs included inthe Multi-TID A-MPDU and requesting BlockAck, the Multi-TID A-MPDUreceiver may ACK using the Per AID TID Info field in which the Block AckStarting Sequence Control field and the Block Ack Bitmap field areomitted with respect to the MPDU corresponding to the MPDU delimiterfield in which the EOF subfield is 0 and the MPDU Length subfield is not0. Specifically, the Multi-TID A-MPDU receiver may ACK using the Per AIDTID Info field in which the Ack Type subfield is set to 1 with respectto the MPDU corresponding to the MPDU delimiter field in which the EOFsubfield is 0 and the MPDU Length subfield is not 0. In theseembodiments, the Multi-TID A-MPDU receiver may set the TID subfield ofthe Per AID TID Info field to the TID of the received MPDU. In aspecific embodiment, the Multi-TID A-MPDU receiver may transmit to theMulti-TID A-MPDU transmitter the Multi-STA BlockAck frame that indicatesthat the Multi-TID A-MPDU receiver receives all the MPDUs of the TIDindicated by the TID subfield of the Per AID TID Info field and includesa Multi-STA BlockAck frame including the Per AID TID Info in which aBlock Ack Starting Sequence Control subfield and a Block Ack Bitmapsubfield are omitted. In this case, the Per AID TID Info field mayfurther include an indicator indicating that all the MPDUs of the TIDindicated by the TID subfield of the Per AID TID Info field arereceived.

The Multi-TID A-MPDU receiver transmits the generated Multi-STA BlockAckframe to the Multi-TID A-MPDU transmitter. When the value of the TIDsubfield of the Per AID TID Info field is 0 to 7 and the value of theAck Type subfield is 1, the Multi-TID transmitter may determine that aMulti-STA BlockAck frame including a Per AID TID Info field is includedin a Multi-TID A-MPDU soliciting a Multi-STA BlockAck frame and theMulti-TID receiver receives a single MPDU or all the MPDUs correspondingto the TID indicated by the TID subfield.

In the embodiment of FIG. 39, the MPDUs not received by the Multi-TIDA-MPDU receiver are MPDUs corresponding to the MPDU delimiter field inwhich the EOF subfield is 1 and the MPDU Length subfield is not 0.Accordingly, the Multi-TID A-MPDU receiver ACKs using the Per AID TIDInfo field in which the Block Ack Starting Sequence Control field andthe Block Ack Bitmap field are omitted, with respect to the MPDUcorresponding to the MPDU delimiter field in which the EOF subfield is 0and the MPDU Length subfield is not 0. Specifically, a Multi-TID A-MPDUreceiver may transmit to a Multi-TID A-MPDU transmitter a Multi-STABlockAck including a Block Ack Starting Sequence Control field and a PerAID TID Info field in which a Block Ack Bitmap field is omitted.

In the embodiment of FIG. 40, the A-MPDU subframe in which the EOFsubfield is set to 0 in the A-MPDU is limited to not being located afterthe A-MPDU subframe in which the EOF subfield is set to 1. The Multi-TIDA-MPDU receiver does not receive the MPDU delimiter field correspondingto the not-received MPDU. Since the value of the EOF subfield of theMPDU delimiter field corresponding to the MPDU located before thenot-received MPDU is 1, the multi-TID A-MPDU receiver may determine thatthe value of the EOF subfield of the not-received MPDU delimiter fieldis 1. Accordingly, the Multi-TID A-MPDU receiver may determine that theMulti-TID A-MPDU receiver receives all the MPDUs corresponding to theMPDU delimiter field in which the EOF subfield is 0 and the MPDU Lengthsubfield is not 0. The Multi-TID A-MPDU receiver ACKs using the Per AIDTID Info field in which the Block Ack Starting Sequence Control fieldand the Block Ack Bitmap field are omitted, with respect to the MPDUcorresponding to the MPDU delimiter field in which the EOF subfield is 0and the MPDU Length subfield is not 0. Specifically, a Multi-TID A-MPDUreceiver may transmit to a Multi-TID A-MPDU transmitter a Multi-STABlockAck including a Block Ack Starting Sequence Control field and a PerAID TID Info field in which a Block Ack Bitmap field is omitted.

FIG. 41 shows the operation of a wireless communication terminalaccording to an embodiment of the present invention.

The wireless communication terminal receives the trigger frametriggering the random access (S4101). The wireless communicationterminal performs random access based on the trigger frame (S4103). Inthis case, the wireless communication terminal may perform random accessaccording to the OBO procedure described above. Specifically, thewireless communication terminal may perform random access according tothe embodiments described with reference to FIG. 6 to FIG. 26.

The wireless communication terminal may set an integer selected from 0to a value equal to or smaller than the OFDMA Contention Window (OCW) asa counter for random access. In this case, the counter for random accessmay be the OBO counter described above. Also, when the wirelesscommunication terminal attempts random access for the first time, thewireless communication terminal receives the OBO related parametersignaled by the base wireless communication terminal, or the wirelesscommunication terminal succeeds in transmission through the randomaccess, the wireless communication terminal may initialize the OBOprocedure. The initialization of the OBO procedure may include at leastone of initialization of a counter for random access and initializationof OCW. Further, when the wireless communication terminal initializesthe OCW, the wireless communication terminal may set the OCW to OCWmin.When the transmission through the random access of the wirelesscommunication terminal fails, the wireless communication terminal mayupdate the value of OCW to (2×OCW+1). In this case, the wirelesscommunication terminal selects a random integer in the updated OCW, andsets the selected integer as a counter for random access. Further, whenthe value of the OCW reaches OCWmax, the wireless communication terminalmay maintain the OCW as OCWmax even if the transmission through therandom access of the wireless communication terminal fails.

The trigger frame may indicate random access using one or more RUsallocated for random access. Specifically, the trigger frame mayindicate one or more RUs allocated for random access. In this case, thewireless communication terminal may decrement the value of the counterfor random access based on one or more RUs allocated for the randomaccess. When the trigger frame indicates the uplink transmission of thewireless communication terminal, the wireless communication terminal maynot decrement the value of the counter based on the trigger frame. Thespecific operation of the wireless communication terminal may be thesame as that in the embodiment described with reference to FIG. 26.

In this case, as described above, the RU is a group of a plurality ofsubcarriers usable for uplink transmission and downlink transmission.

The wireless communication terminal may decrement the value of thecounter for random access based on the capabilities of the wirelesscommunication terminal and one or more RUs allocated for random access.When the value of the counter for random access is 0 or reaches 0, thewireless communication terminal may randomly select one or more RUsallocated for random access.

The wireless communication terminal may perform the random accessoperation according to the capability of the wireless communicationterminal. In such a case, the wireless communication terminal mayoperate as follows.

The wireless communication terminal may decrement the value of thecounter for random access by the number of RUs, through which thewireless communication terminal is capable of transmitting the TB PPDUaccording to the capabilities of the wireless communication terminal,among the one or more RUs allocated for random access. The capabilitiesof the wireless communication terminal may include capabilities relatedto the bandwidth through which the wireless communication terminal iscapable of performing transmission. In addition, the capability of thewireless communication terminal may include capabilities for the lengthof the padding field included in the TB PPDU. In addition, thecapabilities of the wireless communication terminal may includecapabilities for modulation and coding schemes with which the wirelesscommunication terminal is capable of performing transmission. Thecapability of the wireless communication terminal may include thecapacity of the wireless communication terminal related to at least oneof Dual Carrier Modulation (DCM), the number of spatial streams, thelength of a Guard Interval (GI), a Long Training Field (LTF) type,space-tiem block coding (STBC), and transmission power.

When the value of the counter for random access is 0 or reaches 0, thewireless communication terminal may randomly select any one of the RUsthat are allocated for random access and may transmit the TB PPDUaccording to the capability of the wireless communication terminal. Whenthere is no RU through which the wireless communication terminal iscapable of transmitting the TB PPDU among the one or more RUs allocatedfor the random access, the wireless communication terminal may maintainthe counter for random access as 0. Operations related to thecapabilities of the wireless communication terminal may be the same asthose of the wireless communication terminal in the embodiments of FIGS.14 to 21.

The wireless communication terminal may be a wireless communicationterminal unassociated with the base wireless communication terminaltransmitting the trigger frame. In such a case, the wirelesscommunication terminal may operate as follows.

The wireless communication terminal may set the OCW minimum value, whichis a parameter indicating the minimum value of the OCW, to apredetermined value as a default value of the OCW minimum value, and setthe OCW maximum value, which is a parameter indicating the maximum valueof the OCW, to a predetermined value as a default value of the OCWmaximum value. In this case, the value predetermined to the defaultvalue of the OCW minimum value and the value predetermined to thedefault value of the OCW maximum value may not be values designated bythe base wireless communication terminal. The OCW minimum value may beOCWmin as described above. In addition, the OCW maximum value may be OCWmax described above.

When the wireless communication terminal communicates with the basewireless communication terminal transmitting the trigger frame and theother base wireless communication terminal, the wireless communicationterminal may initialize a parameter for random access to anotherwireless communication terminal. The parameters for random access mayinclude a counter for random access, an OCW minimum value, and an OCWmaximum value, which is a parameter indicating the maximum value of theOCW. When the wireless communication terminal communicates with the basewireless communication terminal transmitting the trigger frame, thewireless communication terminal may set the OCW minimum value and theOCW maximum value according to the information received from the basewireless communication terminal transmitting the trigger frame, and whenthe wireless communication terminal communicates with another basewireless communication terminal, the wireless communication terminal mayset the OCW minimum value and the OCW maximum value according to theinformation received from the other base wireless communicationterminals. In this case, the information received by the wirelesscommunication from the base wireless communication terminal transmittingthe trigger frame or the base wireless communication terminal may beinformation on the OBO parameter. Specifically, the information on theOBO parameter may be the UORA parameter set element described above. Thewireless communication terminal may maintain the OBO-related parametersand the OBO procedure for each base wireless communication terminal. Ina specific embodiment, the wireless communication terminal may set anOBO-related parameter for each base wireless communication terminal.Specifically, the wireless communication terminal may set theOBO-related parameters for each base wireless communication terminalbased on the information on the OBO-related parameters received fromeach base wireless communication terminal. The specific operation of thewireless communication terminal unassociated with the base wirelesscommunication terminal may be the same as that in the embodimentdescribed with reference to FIG. 21 to FIG. 25.

The wireless communication terminal may be a wireless communicationterminal associated with the base wireless communication terminaltransmitting the trigger frame. Also, the base wireless communicationterminal transmitting the trigger frame may belong to a multiple BSSIDset. In such a case, the wireless communication terminal may operate asfollows.

The OCW minimum value and the OCW maximum value may be set according toinformation received from other base wireless communication terminalsbelonging to the multiple BSSID set to which the base wirelesscommunication terminal transmitting the trigger frame belongs. In thiscase, the other base wireless communication terminal may be a basewireless communication terminal operating a BSS corresponding to atransmitted BSSID of a multiple BSSID set. Further, the wirelesscommunication terminal may not decrement the value of the counter basedon the trigger frame transmitted from the other base wirelesscommunication terminal. The other base wireless communication terminalmay be a base wireless communication terminal operating a BSScorresponding to a transmitted BSSID of a multiple BSSID set. Theinformation received from the other base wireless communication terminalmay not be the information indicated in the signaling field allocatedonly for the BSS including the wireless communication terminal.Specifically, the signaling field allocated only for the BSS includingthe wireless communication terminal may indicate the nontransmittedprofile described above. In this case, the information may be the UORAparameter set element described above. When a multiple BSSID set isused, the specific operation of the wireless communication terminal maybe the same as that in the embodiment described with reference to FIG.11 to FIG. 13.

The wireless communication terminal may attempt to perform transmissionto the base wireless communication terminal using the selected RU. Inthis case, the wireless communication terminal may determine whether theselected RU is idle, and may transmit a pending frame for a basewireless communication terminal to the base wireless communicationterminal through the selected RU when the selected RU is idle. Inaddition, when the wireless communication terminal determines that thecorresponding RU is busy with any one of a physical carrier sense or avirtual carrier sense, the wireless communication terminal determinesthat the corresponding RU is busy. The physical carrier sense mayinclude a Clear Channel Assessment (CCA). When it is determined that theRU selected by the wireless communication terminal is busy, the wirelesscommunication terminal may maintain the OBO counter as 0 withouttransmitting a pending frame to the base wireless communication.

Although the present invention is described by using wireless LANcommunication as an example, it is not limited thereto and may beapplied to other communication systems such as cellular communication.Additionally, while the method, device, and system of the presentinvention are described in relation to specific embodiments thereof,some or all of the components or operations of the present invention maybe implemented using a computer system having a general purpose hardwarearchitecture.

The features, structures, and effects described in the above embodimentsare included in at least one embodiment of the present invention and arenot necessary limited to one embodiment. Furthermore, features,structures, and effects shown in each embodiment may be combined ormodified in other embodiments by those skilled in the art. Therefore, itshould be interpreted that contents relating to such combination andmodification are included in the range of the present invention.

While the present invention is described mainly based on the aboveembodiments but is not limited thereto, it will be understood by thoseskilled in the art that various changes and modifications are madewithout departing from the scope of the present invention. For example,each component specifically shown in the embodiments may be modified andimplemented. It should be interpreted that differences relating to suchmodifications and application are included in the scope of the presentinvention defined in the appended claims.

The invention claimed is:
 1. A wireless communication terminal thatwirelessly communicates with a base wireless communication terminal, thewireless communication terminal comprising: a transceiver; and aprocessor, wherein the processor is configured to: set an integerselected from a range of 0 to a value equal to or smaller than an OFDMAContention Window (OCW) as a counter for random access, receive atrigger frame for triggering random access using one or more resourceunits (RUs) allocated for the random access from the base wirelesscommunication terminal using the transceiver, decrement a value of thecounter based on the one or more RUs allocated for the random accesswhen the trigger frame does not schedule an uplink transmission of thewireless communication terminal, and attempt transmission to the basewireless communication terminal when the value of the counter is 0 orreaches 0, wherein the RU is a group of a plurality of subcarriersusable for uplink transmission and downlink transmission.
 2. Thewireless communication terminal of claim 1, wherein when the wirelesscommunication terminal is a wireless communication terminal unassociatedwith the base wireless communication terminal, the processor isconfigured to: set an OCW minimum value, which is a parameter indicatinga minimum value of an OCW, to a value predetermined as a default valueof the OCW minimum value, and set an OCW maximum value, which is aparameter indicating a maximum value of an OCW, to a value predeterminedas a default value of the OCW maximum value, wherein the valuepredetermined as the default value of the OCW minimum value and thevalue predetermined as the default value of the OCW maximum value arenot values designated by the base wireless communication terminal. 3.The wireless communication terminal of claim 2, wherein when thewireless communication terminal is a wireless communication terminalunassociated with the base wireless communication terminal and thewireless communication terminal communicates with a different basewireless communication terminal different from the base wirelesscommunication terminal, the processor is configured to initialize aparameter for random access to the different base wireless communicationterminal, wherein the parameter for the random access comprises thecounter, an OCW minimum value, which is a parameter indicating a minimumvalue of the OCW, and an OCW maximum value, which is a parameterindicating a maximum value of the OCW.
 4. The wireless communicationterminal of claim 3, wherein when the wireless communication terminal isa wireless communication terminal unassociated with the base wirelesscommunication terminal, the processor is configured to: set the OCWminimum value and the OCW maximum value according to informationreceived from the base wireless communication terminal when the wirelesscommunication terminal communicates with the base wireless communicationterminal, and set the OCW minimum value and the OCW maximum valueaccording to information received from the different base wirelesscommunication terminal when the wireless communication terminalcommunicates with the different base wireless communication terminal. 5.The wireless communication terminal of claim 4, wherein when thewireless communication terminal is associated to a BSS corresponding toa nontransmitted Basic Service Set Identification (BSSID) of a multipleBSSID set, the processor is configured to set an OCW minimum value,which is a parameter indicating the minimum value of the OCW, and an OCWmaximum value, which is a parameter indicating the maximum value of theOCW, according to UL OFDMA-based Random Access (UORA) parameter setelement from a BSS corresponding to a transmitted BSSID of the multipleBSSID set, wherein the UORA parameter set includes a parameter relatedto the counter.
 6. The wireless communication terminal of claim 5,wherein the processor is configured not to decrement the value of thecounter based on a trigger frame transmitted from the BSS correspondingto the transmitted BS SID of the multiple BS SID set.
 7. The wirelesscommunication terminal of claim 6, wherein the UORA parameter setreceived from the BSS corresponding to the transmitted BS SID is not aUORA parameter set indicated in a signaling field allocated for a BSSincluding the wireless communication terminal.
 8. A method of operatinga wireless communication terminal wirelessly communicating with a basewireless communication terminal, the method comprising: setting aninteger selected from a range of 0 to a value equal to or smaller thanan OFDMA Contention Window (OCW) as a counter for random access,receiving a trigger frame for triggering random access using one or moreresource units (RUs) allocated for the random access from the basewireless communication terminal using the transceiver, decrementing avalue of the counter based on the one or more RUs allocated for therandom access when the trigger frame does not schedule an uplinktransmission of the wireless communication terminal, and attemptingtransmission to the base wireless communication terminal when the valueof the counter is 0 or reaches 0, wherein the RU is a group of aplurality of subcarriers usable for uplink transmission and downlinktransmission.
 9. The method of claim 8, wherein when the wirelesscommunication terminal is a wireless communication terminal unassociatedwith the base wireless communication terminal, the method furthercomprises: setting an OCW minimum value, which is a parameter indicatinga minimum value of the OCW, to a value predetermined as a default valueof the OCW minimum value, and setting an OCW maximum value, which is aparameter indicating a maximum value of the OCW, to a valuepredetermined as a default value of the OCW maximum value, wherein thevalue predetermined as the default value of the OCW minimum value andthe value predetermined as the default value of the OCW maximum valueare not values designated by the base wireless communication terminal.10. The method of claim 8, wherein when the wireless communicationterminal is a wireless communication terminal unassociated with the basewireless communication terminal and the wireless communication terminalcommunicates with a different base wireless communication terminaldifferent from the base wireless communication terminal, the methodfurther comprises: initializing a parameter for random access to thedifferent base wireless communication terminal, wherein the parameterfor the random access comprises the counter, an OCW minimum value, whichis a parameter indicating a minimum value of the OCW, and an OCW maximumvalue, which is a parameter indicating a maximum value of the OCW. 11.The method of claim 10, wherein when the wireless communication terminalis a wireless communication terminal unassociated with the base wirelesscommunication terminal, the method further comprises: setting the OCWminimum value and the OCW maximum value according to informationreceived from the base wireless communication terminal when the wirelesscommunication terminal communicates with the base wireless communicationterminal, and setting the OCW minimum value and the OCW maximum valueaccording to information received from the different base wirelesscommunication terminal when the wireless communication terminalcommunicates with the different base wireless communication terminal.12. The method of claim 8, wherein when the wireless communicationterminal is associated to a BSS corresponding to a nontransmitted BasicService Set Identification (BSSID) of a multiple BSSID set, the methodfurther comprises: setting an OCW minimum value, which is a parameterindicating the minimum value of the OCW, and an OCW maximum value, whichis a parameter indicating the maximum value of the OCW, according to ULOFDMA-based Random Access (UORA) parameter set element from a BSScorresponding to a transmitted BSSID of the multiple BSSID set, whereinthe UORA parameter set includes a parameter related to the counter. 13.The method of claim 12, decrementing a value of the counter based on theone or more RUs allocated for the random access comprises notdecrementing the value of the counter based on a trigger frametransmitted from the BSS corresponding to the transmitted BS SID of themultiple BS SID set.
 14. The method of claim 13, wherein the UORAparameter set received from the BSS corresponding to the transmittedBSSID is not a UORA parameter set indicated in a signaling fieldallocated for a BSS including the wireless communication terminal.